Attention versus memory in prefrontal cortex
Encyclopedia
A widely accepted theory regarding the function of the brain's prefrontal cortex
is that it serves as a store of short-term memory
. This idea was first formulated by Jacobsen, who reported in 1935 that damage to the primate prefrontal cortex caused short-term memory deficits. Karl Pribram
and colleagues (1952) identified the part of the prefrontal cortex responsible for this deficit as area
46
, also known as the dorsolateral prefrontal cortex
(dlPFC). More recently, Goldman-Rakic and colleagues (1993) evoked short-term memory loss in localized regions of space by temporary inactivation of portions of the dlPFC. Once the concept of working memory
(see also Baddeley's model of working memory
) was established in contemporary neuroscience by Baddeley (1986), these neuropsychological findings contributed to the theory that the prefrontal cortex implements working memory and, in some extreme formulations, only working memory. In the 1990s this theory developed a wide following, and it became the predominant theory of PF function, especially for nonhuman primates. The concept of working memory used by proponents of this theory focused mostly on the short-term maintenance of information, and rather less on the manipulation or monitoring of such information or on the use of that information for decisions. Consistent with the idea that the prefrontal cortex functions predominantly in maintenance memory, delay-period activity in the PF has often been interpreted as a memory trace. (The phrase "delay-period activity" applies to neuronal activity that follows the transient presentation of an instruction cue and persists until a subsequent "go" or "trigger" signal.)
To explore alternative interpretations of delay-period activity in the prefrontal cortex, Lebedev et al. (2004) investigated the discharge rates of single prefrontal neurons as monkeys attended to a stimulus marking one location while remembering a different, unmarked location. Both locations served as potential targets of a saccadic eye movement. Although the task made intensive demands on short-term memory, the largest proportion of prefrontal neurons represented attended locations, not remembered ones. These findings showed that short-term memory functions cannot account for all, or even most, delay-period activity in the part of the prefrontal cortex explored. The authors suggested that prefrontal activity during the delay-period contributes more to the process of attentional selection (and selective attention) than to memory storage.
Lebedev et al. experiment that dissociated representation of spatial attention
from representation of spatial memory
in prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
is that it serves as a store of short-term memory
Short-term memory
Short-term memory is the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory is believed to be in the order of seconds. A commonly cited capacity is 7 ± 2 elements...
. This idea was first formulated by Jacobsen, who reported in 1935 that damage to the primate prefrontal cortex caused short-term memory deficits. Karl Pribram
Karl H. Pribram
Karl H. Pribram is a professor at Georgetown University, in the United States, and an emeritus professor of psychology and psychiatry at Stanford University and Radford University...
and colleagues (1952) identified the part of the prefrontal cortex responsible for this deficit as area
Brodmann area
A Brodmann area is a region of the cerebral cortex defined based on its cytoarchitectonics, or structure and organization of cells.-History:...
46
Brodmann area 46
Brodmann area 46, or BA46, is part of the frontal cortex in the human brain. It is between BA10 and BA45.BA46 is known as middle frontal area 46. In the human brain it occupies approximately the middle third of the middle frontal gyrus and the most rostral portion of the inferior frontal gyrus...
, also known as the dorsolateral prefrontal cortex
Dorsolateral prefrontal cortex
The dorsolateral prefrontal cortex , according to a more restricted definition, is roughly equivalent to Brodmann areas 9 and 46. According to a broader definition DL-PFC consists of the lateral portions of Brodmann areas 9 – 12, of areas 45, 46, and the superior part of area 47. These regions...
(dlPFC). More recently, Goldman-Rakic and colleagues (1993) evoked short-term memory loss in localized regions of space by temporary inactivation of portions of the dlPFC. Once the concept of 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...
(see also Baddeley's model of working memory
Baddeley's Model of Working Memory
Alan Baddeley and Graham Hitch proposed a model of working memory in 1974, in an attempt to describe a more accurate model of short-term memory....
) was established in contemporary neuroscience by Baddeley (1986), these neuropsychological findings contributed to the theory that the prefrontal cortex implements working memory and, in some extreme formulations, only working memory. In the 1990s this theory developed a wide following, and it became the predominant theory of PF function, especially for nonhuman primates. The concept of working memory used by proponents of this theory focused mostly on the short-term maintenance of information, and rather less on the manipulation or monitoring of such information or on the use of that information for decisions. Consistent with the idea that the prefrontal cortex functions predominantly in maintenance memory, delay-period activity in the PF has often been interpreted as a memory trace. (The phrase "delay-period activity" applies to neuronal activity that follows the transient presentation of an instruction cue and persists until a subsequent "go" or "trigger" signal.)
To explore alternative interpretations of delay-period activity in the prefrontal cortex, Lebedev et al. (2004) investigated the discharge rates of single prefrontal neurons as monkeys attended to a stimulus marking one location while remembering a different, unmarked location. Both locations served as potential targets of a saccadic eye movement. Although the task made intensive demands on short-term memory, the largest proportion of prefrontal neurons represented attended locations, not remembered ones. These findings showed that short-term memory functions cannot account for all, or even most, delay-period activity in the part of the prefrontal cortex explored. The authors suggested that prefrontal activity during the delay-period contributes more to the process of attentional selection (and selective attention) than to memory storage.
Lebedev et al. experiment that dissociated representation of spatial attention
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
from representation of spatial memory
Spatial memory
In cognitive psychology and neuroscience, spatial memory is the part of memory responsible for recording information about one's environment and its spatial orientation. For example, a person's spatial memory is required in order to navigate around a familiar city, just as a rat's spatial memory is...
in prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
Further reading
- Baddeley A. (1986) Working memory. Oxford: Oxford University Press. 289 p.
- Funahashi S., Bruce C.J., Goldman-Rakic P.S. (1993a) Dorsolateral prefrontal lesions and oculomotor delayed-response performance: Evidence for mnemonic “scotomas.”. J Neurosci 13: 1479–1497.
- Jacobsen C.F. (1936) Studies of cerebral function in primates. I. The functions of the frontal associations areas in monkeys. Comp Psychol Monogr 13: 3–60.
- Lebedev M.A., Messinger A., Kralik J.D., Wise S.P. (2004) Representation of attended versus remembered locations in prefrontal cortex. PLoS Biology, 2: 1919-1935.
- Postle B.R., Druzgal T.J., D'Esposito M. (2003) Seeking the neural substrates of visual working memory storage. Cortex 39: 927–946.
- Pribram K.H., Mishkin M., Rosvold H.E., Kaplan S.J. (1952) Effects of delayed-response performance of lesions of dorsolateral and ventromedial frontal cortex of baboons. J Comp Physiol Psychol 45: 565–575.