Neuroanatomy of memory
Encyclopedia
The neuroanatomy of memory
encompasses a wide variety of anatomical structures in the brain
.
The hippocampus
is a structure in the brain that has been associated with various memory functions. It is part of the limbic system
, and lies next to the medial temporal lobe. It is made up of two structures, the Ammon’s Horn, and the Dentate gyrus
, each containing different types of cells
.
s in humans. In one study, single-cell recordings were taken from electrodes implanted in a rat’s hippocampus, and it was found that certain neurons responded strongly only when the rat was in certain locations. These cells are called place cells, and collections of these cells can be considered to be mental maps. Individual place cells do not only respond to one unique area only however, the patterns of activation of these cells overlap to form layered mental maps within the hippocampus. A good analogy is the example of the same television or computer screen pixels being used to light up any trillions of possible combinations to produce images, just as the place cells can be used in any multiple possible combinations to represent mental maps. The hippocampus’ right side is more oriented towards responding to spatial aspects, whereas the left side is associated with other context information. Also, there is evidence that experience in building extensive mental maps, such as driving a city taxi for a long time (since this requires a lot of memorization of routes), can increase the volume of one’s hippocampus.
, the inability to form new memories. This implies that the hippocampus is important not only for storing cognitive maps, but for encoding memories
.
The hippocampus is also involved in memory consolidation
, the slow process by which memories are converted from short to long term memory. This is supported by studies in which lesions are applied to rat hippocampi at different times after learning. The process of consolidation may take up to a couple years.
It has also been found that it is possible to form new semantic memories without the hippocampus, but not episodic memories, which means that explicit descriptions of actual events (episodic) cannot be learned, but some meaning and knowledge is gained from experiences (semantic).
The cerebellum
("little brain") is a structure located at the rear of the brain, near the spinal cord
. It looks like a miniature version of the cerebral cortex
, in that it has a wavy, or convoluted surface.
Unlike the hippocampus which is involved in the encoding of complex memories, the cerebellum plays a role in the learning of procedural memory
, and motor learning, such as skills requiring co-ordination and fine motor control. An example of a skill requiring procedural memory would be playing a musical instrument, or driving a car or riding a bike. Individuals with transient global amnesia
that have difficulty forming new memories and/or remembering old events may sometimes retain the ability to perform complex musical pieces, suggesting that procedural memory is completely dissociated from conscious memory, also known as explicit memory
.
This separation makes sense if the cerebellum, which is far removed from the hippocampus, is responsible for procedural learning. The cerebellum is more generally involved in motor learning, and damage to it can result in problems with movement, specifically it is considered to co-ordinate timing and accuracy of movements, and to make long-term changes (learning) to improve these skills.
Located below the hippocampus in the medial temporal lobes are two amygdalae (singular "amygdala"). The amygdala are associated with both emotional learning and memory, as it responds strongly to emotional stimuli, especially fear. These neurons assist in encoding emotional memories and enhancing them. This process results in emotional events being more deeply and accurately encoded into memory. Lesions to the amygdalae in monkeys have been shown to impair motivation, as well as the processing of emotions.
The amygdala is involved in memory consolidation
, which is the process of transferring information that is currently in working memory into ones long-term memory. This process is also known as memory modulation. The amygdala works to encode recent emotional information into memory. Memory research has shown that the greater ones emotional arousal level at the time of the event, the greater the chance that the event will be remembered. This may be due to the amygdala enhancing the emotional aspect of the information during encoding, causing the memory to be processed at a deeper level and therefore, more likely to withstand forgetting.
The basal ganglia
are a group of nuclei
which are located in the medial temporal lobe, above the thalamus
and connected to the cerebral cortex. Specifically, the basal ganglia includes the subthalamic nucleus
, substantia nigra
, the globus pallidus
, the ventral striatum
and the dorsal striatum
, which consists of the putamen
and the caudate nucleus
. The basic functions of these nuclei deal with cognition, learning, and motor control and activities. The basal ganglia are also associated with learning, memory, and unconscious memory processes, such as motor skills and implicit memory
.
The caudate nucleus is thought to assist in learning and memory of associations taught during operant conditioning
. Specifically, research has shown that this part of the basal ganglia plays a role in acquiring stimulus-response habits, as well as in solving sequence tasks.
Damage to the basal ganglia has been linked to dysfunctional learning of motor and perceptual-motor skills. Most disorders that are associated with damage to these areas of the brain involve some type of motor dysfunction, as well as trouble with mental switching between tasks in working memory
. Such symptoms are often present in those who suffer from dystonia
, athymhormic syndrome
, Fahr's syndrome
, Huntington's disease
or Parkinson's disease
. Huntington's and Parkinson's disease involve both motor deficits and cognitive impairment.
and positioned anterior to the parietal lobes. It is separated from the parietal lobe by the primary motor cortex
, which controls voluntary movements of specific body parts associated with the precentral gyrus. The cortex here serves our ability to plan the day, organize work, type a letter, pay attention to details and control the movements of your arms and legs. It also contributed to your personality and behaviour.
When considering the frontal lobes in regards to memory
, we see that it is very important in the coordination
of information. Therefore, the frontal lobes are important in working memory
. For example, when you are thinking about how to get to a mall you have never been to before, you combine various bits of knowledge you already have: the layout of the city the mall is in, information from a map, knowledge of traffic patterns in that area and conversations with your friends about the location of the mall. By actively using all of this information, you can determine the best route for you to take. This action involves the controlled use of information in working memory, coordinated by the frontal lobes.
The frontal lobes help a person select out memories that are most relevant on a given occasion. It can coordinate various types of information into a coherent memory trace. For example, the knowledge of the information itself, as well as knowing where information came from must be put together into a single memory representation; this is called source monitoring. Sometimes we experience situations where information becomes separated, such as when we recall something, but cannot remember where we remember it from; this is referred to as a source monitoring error.
The frontal lobes are also involved in the ability to remember what we need to do in the future; this is called prospective memory
.
that is located beneath the Sylvian fissure on both the left and right hemispheres of the brain. Lobes in this cortex are more closely associated with memory and in particular autobiographical memory
.
The temporal lobes are also concerned with recognition memory. This is the capacity to identify an item as one that was recently encountered. Recognition memory is widely viewed as consisting of two components, a familiarity component (i.e. Do I know this person waving at me?) and a recollective component (i.e. That is my friend Julia, from evolutionary psychology class).
Damage to the temporal lobe can affect an individual in a litany of ways ranging from: disturbance of auditory sensation and perception, disturbance of selective attention of auditory and visual input, disorders of visual perception, impaired organization and categorization of verbal material, disturbance of language comprehension, and altered personality.
In regard to memory, temporal lobe damage can impair long-term memory
. Thus, general semantic knowledge or more personal episodic memories of one’s childhood could be affected.
, superior to the occipital lobe and posterior to the frontal lobe, visually at the top of the back of the head. The make up of the parietal lobe is defined by four anatomical boundaries in the brain, providing a division of all the four lobes.
The parietal lobe has many functions and duties in the brain and its main functioning can be divided down into two main areas: (1) sensation and perception (2) constructing a spatial coordinate system to represent the world around us. The parietal lobe helps us to mediate attention when necessary and provides spatial awareness and navigational skills. Also, it integrates all of our sensory information (touch, sight, pain etc.) to form a single perception. Parietal lobe gives the ability to focus our attention on different stimuli at the same time, PET scans show high activity in the parietal lobe when participates being studied were asked to focus their attention at two separate areas of attention. Parietal lobe also assists with verbal short term memory and damage to the supramarginal gyrus cause short term memory loss.
Damage to the parietal lobe results in the syndrome ‘neglect’ which is when patients treat part of their body or objects in their visual field as though it never existed. Damage to the left side of the parietal lobe can result in what is called Gerstmann syndrome
. It includes right-left confusion, difficulty with writing (agraphia) and difficulty with mathematics (acalculia
). It can also produce disorders of language (aphasia
) and the inability to perceive objects. Damage to the right parietal lobe can result in neglecting part of the body or space (contralateral neglect), which can impair many self-care skills such as dressing and washing. Right side damage can also cause difficulty in making things (constructional apraxia
), denial of deficits (anosagnosia) and drawing ability. Neglect syndrome tends to be more prevalent on the right side of the parietal lobe, because the right mediates attention to both the left and right fields. Damage in the somatic sensory cortex results in loss of perception of bodily sensations, namely sense of touch.
system, the main function of the occipital lobe is that of vision.
Retinal sensors send signals through the optic tract to the Lateral geniculate nucleus
. Once the Lateral Geniculate Nucleus receives the information it is sent down the primary visual cortex where it is organized and sent down one of two possible path ways; dorsal
or ventral stream. The ventral stream is responsible for object representation and recognition and is also commonly known as the "what" stream. The dorsal stream is responsible for guiding our actions and recognizing where objects are in space, commonly known as the "where" or "how" stream. Once in the information is organized and send through the pathways it continues to the other areas of the brain responsible for visual processing.
The most important function of the Occipital lobe is vision. Due to the positioning of this lobe at the back of the head it is not susceptible to much injury but any significant damage to the brain can cause a variety of damage to our visual perception system. Common problems in the occipital lobe are field defects and scotoma
s, movement and colour discrimination, hallucinations, illusions, inability to recognize words and inability to recognize movement. A study was done in which patients suffered from a tumour on the occipital lobe and the results shows that the most frequent consequence was contralateral damage to the visual field. When damage occurs in the occipital lobe it is most common to see the effects on the opposite side of the brain. Since the brain regions are so specialized in their functioning damages done to specific areas of the brain can cause specific type of damage. Damage to the left side of the brain can lead to language discrepancies, i.e. difficulty in properly identifying letters, numbers and words, inability to incorporate visual stimuli to comprehend multiple ways an object can be found. Right side damage causes non-verbal problems, i.e. identifying geometric shapes, perception of figures and faces. In almost all regions of the brain left side damage leads to general language problems where as right side damage leads to general perception and problem solving skills.
(FTLD) is a common form of dementia
due to the degeneration of the frontal and temporal lobes. Studies have found significant decreases in the essential needs for proper functioning in these lobes. The autobiographical domain in memory
is largely affected by this disease. In one study, FTLD patients were interviewed and asked to describe a significant event from five different periods of their lives. Using the interview and different methods of imaging, the experimenters hoped to find links between patterns of brain volume loss and performance in the interview.
Through image processing, patterns of significant reduced parenchymal volumes that encompass the frontal and temporal lobes were found. Through comparison to a control group of patients it was found that parenchymal volumes increased during episodic recall, and decreased during semantic recall. The experimenters discussed that lifespan autobiographical episodic recall was largely damaged in FTLD patients and semantic autobiographical memory seemed to be spared.
involves both damage to the basal ganglia and certain memory dysfunctions, suggesting that the basal ganglia are involved in specific types of memory. Those who have this disease have problems with both their working memory and spatial memory.
Most people can instantly and easily use visual-spatial memory to remember locations and pictures, but a person with Parkinson's disease would find this difficult. He or she would also have trouble encoding this visual and spatial information into long-term memory. This suggests that the basal ganglia work in both encoding and recalling spatial information.
People with Parkinson's disease display working memory impairment during sequence tasks and tasks involving events in time. They also have difficulty in knowing how to use their memory, such as when to change strategies or maintain a train of thought.
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
encompasses a wide variety of anatomical structures in the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
.
Hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
is a structure in the brain that has been associated with various memory functions. It is part of the limbic system
Limbic system
The limbic system is a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, septum, limbic cortex and fornix, which seemingly support a variety of functions including emotion, behavior, long term memory, and olfaction. The term "limbic" comes from the Latin...
, and lies next to the medial temporal lobe. It is made up of two structures, the Ammon’s Horn, and the Dentate gyrus
Dentate gyrus
The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories as well as other functional roles. It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult rats, .The dentate gyrus cells receive...
, each containing different types of cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
Cognitive maps
There is evidence that the hippocampus contains cognitive mapCognitive map
Cognitive maps are a type of mental processing composed of a series of psychological transformations by which an individual can acquire, code, store, recall, and decode information about the relative locations and attributes of phenomena in their everyday or metaphorical spatial environment.The...
s in humans. In one study, single-cell recordings were taken from electrodes implanted in a rat’s hippocampus, and it was found that certain neurons responded strongly only when the rat was in certain locations. These cells are called place cells, and collections of these cells can be considered to be mental maps. Individual place cells do not only respond to one unique area only however, the patterns of activation of these cells overlap to form layered mental maps within the hippocampus. A good analogy is the example of the same television or computer screen pixels being used to light up any trillions of possible combinations to produce images, just as the place cells can be used in any multiple possible combinations to represent mental maps. The hippocampus’ right side is more oriented towards responding to spatial aspects, whereas the left side is associated with other context information. Also, there is evidence that experience in building extensive mental maps, such as driving a city taxi for a long time (since this requires a lot of memorization of routes), can increase the volume of one’s hippocampus.
Encoding
Damage to the hippocampus and surrounding area can cause anterograde amnesiaAnterograde amnesia
Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
, the inability to form new memories. This implies that the hippocampus is important not only for storing cognitive maps, but for encoding memories
Encoding (Memory)
Memory has the ability to encode, store and recall information. Memories give an organism the capability to learn and adapt from previous experiences as well as build relationships. Encoding allows the perceived item of use or interest to be converted into a construct that can be stored within the...
.
The hippocampus is also involved in memory consolidation
Memory consolidation
Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...
, the slow process by which memories are converted from short to long term memory. This is supported by studies in which lesions are applied to rat hippocampi at different times after learning. The process of consolidation may take up to a couple years.
It has also been found that it is possible to form new semantic memories without the hippocampus, but not episodic memories, which means that explicit descriptions of actual events (episodic) cannot be learned, but some meaning and knowledge is gained from experiences (semantic).
Cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
("little brain") is a structure located at the rear of the brain, near the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. It looks like a miniature version of the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
, in that it has a wavy, or convoluted surface.
Unlike the hippocampus which is involved in the encoding of complex memories, the cerebellum plays a role in the learning of procedural memory
Procedural memory
Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...
, and motor learning, such as skills requiring co-ordination and fine motor control. An example of a skill requiring procedural memory would be playing a musical instrument, or driving a car or riding a bike. Individuals with transient global amnesia
Transient global amnesia
Transient global amnesia is a syndrome in clinical neurology whose key defining characteristic is temporary but almost total disruption of short-term memory with a range of problems accessing older memories...
that have difficulty forming new memories and/or remembering old events may sometimes retain the ability to perform complex musical pieces, suggesting that procedural memory is completely dissociated from conscious memory, also known as explicit memory
Explicit memory
Explicit memory is the conscious, intentional recollection of previous experiences and information. People use explicit memory throughout the day, such as remembering the time of an appointment or recollecting an event from years ago....
.
This separation makes sense if the cerebellum, which is far removed from the hippocampus, is responsible for procedural learning. The cerebellum is more generally involved in motor learning, and damage to it can result in problems with movement, specifically it is considered to co-ordinate timing and accuracy of movements, and to make long-term changes (learning) to improve these skills.
Amygdala
Memory of fear conditioning
Pavlovian conditioning tests have shown the active role of the amygdala in fear conditioning in rats. Research involving lesions to the basolateral nucleus have shown a strong association with memories involving fear. The central nucleus is linked with the behavioral responses that are dependent on the basolateral’s reaction to fear. The central nucleus of the amygdala is also linked to emotions and behaviors motivated by food and sex.Memory consolidation
Emotional experiences and events are somewhat fragile and take a while to be completely set into memory. This slow process, referred to as consolidation, allows emotions to influence the way the memory is stored.The amygdala is involved in memory consolidation
Memory consolidation
Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...
, which is the process of transferring information that is currently in working memory into ones long-term memory. This process is also known as memory modulation. The amygdala works to encode recent emotional information into memory. Memory research has shown that the greater ones emotional arousal level at the time of the event, the greater the chance that the event will be remembered. This may be due to the amygdala enhancing the emotional aspect of the information during encoding, causing the memory to be processed at a deeper level and therefore, more likely to withstand forgetting.
Basal ganglia and motor memory
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
are a group of nuclei
Nucleus (neuroanatomy)
In neuroanatomy, a nucleus is a brain structure consisting of a relatively compact cluster of neurons. It is one of the two most common forms of nerve cell organization, the other being layered structures such as the cerebral cortex or cerebellar cortex. In anatomical sections, a nucleus shows up...
which are located in the medial temporal lobe, above the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
and connected to the cerebral cortex. Specifically, the basal ganglia includes the subthalamic nucleus
Subthalamic nucleus
The subthalamic nucleus is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system. Anatomically, it is the major part of subthalamus. As suggested by its name, the subthalamic nucleus is located ventral to the thalamus. It is also...
, substantia nigra
Substantia nigra
The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...
, the globus pallidus
Globus pallidus
The globus pallidus also known as paleostriatum, is a sub-cortical structure of the brain. Topographically, it is part of the telencephalon, but retains close functional ties with the subthalamus - both of which are part of the extrapyramidal motor system...
, the ventral striatum
Ventral striatum
The ventral striatum is generally considered that part of the striatum that is connectionally associated with limbic structures, such as the amygdala, hippocampus, midline thalamus, and certain regions of the prefrontal cortex...
and the dorsal striatum
Dorsal striatum
The dorsal striatum, corpus striatum or striated body is a compound structure consisting of the caudate nucleus, and the lentiform nucleus...
, which consists of the putamen
Putamen
The putamen is a round structure located at the base of the forebrain . The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that comprises the basal ganglia. Through various pathways, the putamen is connected to the substantia nigra and globus pallidus...
and the caudate nucleus
Caudate nucleus
The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system.-Anatomy:...
. The basic functions of these nuclei deal with cognition, learning, and motor control and activities. The basal ganglia are also associated with learning, memory, and unconscious memory processes, such as motor skills and implicit memory
Implicit memory
Implicit memory is a type of memory in which previous experiences aid in the performance of a task without conscious awareness of these previous experiences. Evidence for implicit memory arises in priming, a process whereby subjects show improved performance on tasks for which they have been...
.
The caudate nucleus is thought to assist in learning and memory of associations taught during operant conditioning
Operant conditioning
Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...
. Specifically, research has shown that this part of the basal ganglia plays a role in acquiring stimulus-response habits, as well as in solving sequence tasks.
Damage to the basal ganglia has been linked to dysfunctional learning of motor and perceptual-motor skills. Most disorders that are associated with damage to these areas of the brain involve some type of motor dysfunction, as well as trouble with mental switching between tasks in working memory
Working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...
. Such symptoms are often present in those who suffer from dystonia
Dystonia
Dystonia is a neurological movement disorder, in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The disorder may be hereditary or caused by other factors such as birth-related or other physical trauma, infection, poisoning or reaction to...
, athymhormic syndrome
Athymhormic syndrome
Athymhormic syndrome, or psychic akinesia, is a rare neurological syndrome characterized by extreme passivity, apathy, blunted affect, and a profound generalized loss of self-motivation and conscious thought. For example, a patient with this syndrome might sustain severe burns on contact with a hot...
, Fahr's syndrome
Fahr's syndrome
Idiopathic Basal Ganglia Calcification, also known as Fahr disease or Fahr’s Syndrome is a rare, genetically dominant, inherited neurological disorder characterized by abnormal deposits of calcium in areas of the brain that control movement, including the basal ganglia and the cerebral cortex...
, Huntington's disease
Huntington's disease
Huntington's disease, chorea, or disorder , is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and dementia. It typically becomes noticeable in middle age. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea...
or Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
. Huntington's and Parkinson's disease involve both motor deficits and cognitive impairment.
Frontal lobe
The frontal lobes are located at the front of each cerebral hemisphereCerebral hemisphere
A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...
and positioned anterior to the parietal lobes. It is separated from the parietal lobe by the primary motor cortex
Primary motor cortex
The primary motor cortex is a brain region that in humans is located in the posterior portion of the frontal lobe. Itworks in association with pre-motor areas to plan and execute movements. M1 contains large neurons known as Betz cells, which send long axons down the spinal cord to synapse onto...
, which controls voluntary movements of specific body parts associated with the precentral gyrus. The cortex here serves our ability to plan the day, organize work, type a letter, pay attention to details and control the movements of your arms and legs. It also contributed to your personality and behaviour.
When considering the frontal lobes in regards to memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
, we see that it is very important in the coordination
Coordination
Coordination is the act of coordinating, making different people or things work together for a goal or effect to fulfill desired goals in an organization.Coordination is a managerial function in which different activities of the business are properly adjusted and interlinked.Coordination may also...
of information. Therefore, the frontal lobes are important in working memory
Working memory
Working memory has been defined as the system which actively holds information in the mind to do verbal and nonverbal tasks such as reasoning and comprehension, and to make it available for further information processing...
. For example, when you are thinking about how to get to a mall you have never been to before, you combine various bits of knowledge you already have: the layout of the city the mall is in, information from a map, knowledge of traffic patterns in that area and conversations with your friends about the location of the mall. By actively using all of this information, you can determine the best route for you to take. This action involves the controlled use of information in working memory, coordinated by the frontal lobes.
The frontal lobes help a person select out memories that are most relevant on a given occasion. It can coordinate various types of information into a coherent memory trace. For example, the knowledge of the information itself, as well as knowing where information came from must be put together into a single memory representation; this is called source monitoring. Sometimes we experience situations where information becomes separated, such as when we recall something, but cannot remember where we remember it from; this is referred to as a source monitoring error.
The frontal lobes are also involved in the ability to remember what we need to do in the future; this is called prospective memory
Prospective memory
Prospective memory is a form of memory that involves remembering to perform a planned action or intention at the appropriate time. Prospective memory tasks are highly prevalent in daily life and range from relatively simple tasks to extreme life-or-death situations...
.
Temporal lobe
The temporal lobes are a region of the cerebral cortexCerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
that is located beneath the Sylvian fissure on both the left and right hemispheres of the brain. Lobes in this cortex are more closely associated with memory and in particular autobiographical memory
Autobiographical memory
Autobiographical memory is a memory system consisting of episodes recollected from an individual's life, based on a combination of episodic and semantic memory.-Formation:Conway and Pleydell-Pearce proposed that autobiographical...
.
The temporal lobes are also concerned with recognition memory. This is the capacity to identify an item as one that was recently encountered. Recognition memory is widely viewed as consisting of two components, a familiarity component (i.e. Do I know this person waving at me?) and a recollective component (i.e. That is my friend Julia, from evolutionary psychology class).
Damage to the temporal lobe can affect an individual in a litany of ways ranging from: disturbance of auditory sensation and perception, disturbance of selective attention of auditory and visual input, disorders of visual perception, impaired organization and categorization of verbal material, disturbance of language comprehension, and altered personality.
In regard to memory, temporal lobe damage can impair long-term memory
Long-term memory
Long-term memory is memory in which associations among items are stored, as part of the theory of a dual-store memory model. According to the theory, long term memory differs structurally and functionally from working memory or short-term memory, which ostensibly stores items for only around 20–30...
. Thus, general semantic knowledge or more personal episodic memories of one’s childhood could be affected.
Parietal lobe
The parietal lobe is located directly behind the central sulcusCentral sulcus
-External links:* via the Neuroscience Information Framework...
, superior to the occipital lobe and posterior to the frontal lobe, visually at the top of the back of the head. The make up of the parietal lobe is defined by four anatomical boundaries in the brain, providing a division of all the four lobes.
The parietal lobe has many functions and duties in the brain and its main functioning can be divided down into two main areas: (1) sensation and perception (2) constructing a spatial coordinate system to represent the world around us. The parietal lobe helps us to mediate attention when necessary and provides spatial awareness and navigational skills. Also, it integrates all of our sensory information (touch, sight, pain etc.) to form a single perception. Parietal lobe gives the ability to focus our attention on different stimuli at the same time, PET scans show high activity in the parietal lobe when participates being studied were asked to focus their attention at two separate areas of attention. Parietal lobe also assists with verbal short term memory and damage to the supramarginal gyrus cause short term memory loss.
Damage to the parietal lobe results in the syndrome ‘neglect’ which is when patients treat part of their body or objects in their visual field as though it never existed. Damage to the left side of the parietal lobe can result in what is called Gerstmann syndrome
Gerstmann syndrome
Gerstmann syndrome is a neurological disorder that is characterized by a constellation of symptoms that suggests the presence of a lesion in a particular area of the brain...
. It includes right-left confusion, difficulty with writing (agraphia) and difficulty with mathematics (acalculia
Acalculia
Acalculia is an acquired impairment in which patients have difficulty performing simple mathematical tasks, such as adding, subtracting, multiplying and even simply stating which of two numbers is larger...
). It can also produce disorders of language (aphasia
Aphasia
Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....
) and the inability to perceive objects. Damage to the right parietal lobe can result in neglecting part of the body or space (contralateral neglect), which can impair many self-care skills such as dressing and washing. Right side damage can also cause difficulty in making things (constructional apraxia
Apraxia
Apraxia is a disorder caused by damage to specific areas of the cerebrum. Apraxia is characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements...
), denial of deficits (anosagnosia) and drawing ability. Neglect syndrome tends to be more prevalent on the right side of the parietal lobe, because the right mediates attention to both the left and right fields. Damage in the somatic sensory cortex results in loss of perception of bodily sensations, namely sense of touch.
Occipital lobe
The occipital lobe is the smallest of all four lobes in the human cerebral cortex and located in the rearmost part of the skull and considered to be part of the forebrain. The occipital lobe sits directly above the cerebellum and is situated posterior to the Parieto-occipital sulcus, or parieto-occipital sulcus. This lobe is known as the centre of the visual perceptionVisual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
system, the main function of the occipital lobe is that of vision.
Retinal sensors send signals through the optic tract to the Lateral geniculate nucleus
Lateral geniculate nucleus
The lateral geniculate nucleus is the primary relay center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain....
. Once the Lateral Geniculate Nucleus receives the information it is sent down the primary visual cortex where it is organized and sent down one of two possible path ways; dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
or ventral stream. The ventral stream is responsible for object representation and recognition and is also commonly known as the "what" stream. The dorsal stream is responsible for guiding our actions and recognizing where objects are in space, commonly known as the "where" or "how" stream. Once in the information is organized and send through the pathways it continues to the other areas of the brain responsible for visual processing.
The most important function of the Occipital lobe is vision. Due to the positioning of this lobe at the back of the head it is not susceptible to much injury but any significant damage to the brain can cause a variety of damage to our visual perception system. Common problems in the occipital lobe are field defects and scotoma
Scotoma
A scotoma is an area of partial alteration in one's field of vision consisting of a partially diminished or entirely degenerated visual acuity which is surrounded by a field of normal - or relatively well-preserved - vision.Every normal mammalian eye has a scotoma in its field of vision, usually...
s, movement and colour discrimination, hallucinations, illusions, inability to recognize words and inability to recognize movement. A study was done in which patients suffered from a tumour on the occipital lobe and the results shows that the most frequent consequence was contralateral damage to the visual field. When damage occurs in the occipital lobe it is most common to see the effects on the opposite side of the brain. Since the brain regions are so specialized in their functioning damages done to specific areas of the brain can cause specific type of damage. Damage to the left side of the brain can lead to language discrepancies, i.e. difficulty in properly identifying letters, numbers and words, inability to incorporate visual stimuli to comprehend multiple ways an object can be found. Right side damage causes non-verbal problems, i.e. identifying geometric shapes, perception of figures and faces. In almost all regions of the brain left side damage leads to general language problems where as right side damage leads to general perception and problem solving skills.
Damage to the cortex
Many studies of different disease and disorders that have symptoms of memory loss have provided reinforcing evidence to the study of the anatomy of the brain and which parts are more utilized in memory.Frontotemporal lobar degeneration and memory
Frontotemporal lobar degenerationFrontotemporal lobar degeneration
-Further reading:*Hodges, John R. The Frontotemporal Dementia Syndromes. Cambridge University Press. 2007 ISBN 978-0-521-85477-1-External links:****Mayo Clinic - **...
(FTLD) is a common form of dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...
due to the degeneration of the frontal and temporal lobes. Studies have found significant decreases in the essential needs for proper functioning in these lobes. The autobiographical domain in memory
Autobiographical memory
Autobiographical memory is a memory system consisting of episodes recollected from an individual's life, based on a combination of episodic and semantic memory.-Formation:Conway and Pleydell-Pearce proposed that autobiographical...
is largely affected by this disease. In one study, FTLD patients were interviewed and asked to describe a significant event from five different periods of their lives. Using the interview and different methods of imaging, the experimenters hoped to find links between patterns of brain volume loss and performance in the interview.
Through image processing, patterns of significant reduced parenchymal volumes that encompass the frontal and temporal lobes were found. Through comparison to a control group of patients it was found that parenchymal volumes increased during episodic recall, and decreased during semantic recall. The experimenters discussed that lifespan autobiographical episodic recall was largely damaged in FTLD patients and semantic autobiographical memory seemed to be spared.
Parkinson's disease and memory
Parkinson's diseaseParkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
involves both damage to the basal ganglia and certain memory dysfunctions, suggesting that the basal ganglia are involved in specific types of memory. Those who have this disease have problems with both their working memory and spatial memory.
Most people can instantly and easily use visual-spatial memory to remember locations and pictures, but a person with Parkinson's disease would find this difficult. He or she would also have trouble encoding this visual and spatial information into long-term memory. This suggests that the basal ganglia work in both encoding and recalling spatial information.
People with Parkinson's disease display working memory impairment during sequence tasks and tasks involving events in time. They also have difficulty in knowing how to use their memory, such as when to change strategies or maintain a train of thought.