Neural mechanisms for visual memory and their role in attention - PubMed (original) (raw)

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Neural mechanisms for visual memory and their role in attention

R Desimone. Proc Natl Acad Sci U S A. 1996.

Abstract

Recent studies show that neuronal mechanisms for learning and memory both dynamically modulate and permanently alter the representations of visual stimuli in the adult monkey cortex. Three commonly observed neuronal effects in memory-demanding tasks are repetition suppression, enhancement, and delay activity. In repetition suppression, repeated experience with the same visual stimulus leads to both short- and long-term suppression of neuronal responses in subpopulations of visual neurons. Enhancement works in an opposite fashion, in that neuronal responses are enhanced for objects with learned behavioral relevance. Delay activity is found in tasks in which animals are required to actively hold specific information "on-line" for short periods. Repetition suppression appears to be an intrinsic property of visual cortical areas such as inferior temporal cortex and is thought to be important for perceptual learning and priming. By contrast, enhancement and delay activity may depend on feedback to temporal cortex from prefrontal cortex and are thought to be important for working memory. All of these mnemonic effects on neuronal responses bias the competitive interactions that take place between stimulus representations in the cortex when there is more than one stimulus in the visual field. As a result, memory will often determine the winner of these competitions and, thus, will determine which stimulus is attended.

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Figures

Figure 1

Figure 1

Five ways in which neuronal activity is modified during the formation or expression of memory traces. (Adapted from ref. .)

Figure 2

Figure 2

Response histograms averaged from a population of 40 prefrontal neurons that had significant sample-selective delay activity. Responses are shown separately for trials in which a preferred or “good” stimulus was used as the sample and trials in which a nonpreferred or “poor” stimulus was used as the sample (bin width, 40 ms). (Adapted from ref. .)

Figure 3

Figure 3

Response histograms averaged from a population of 22 IT neurons recorded while the monkey performed a visual search task. A cue stimulus was briefly presented at the start of the trial, followed by a blank delay period during which the animal maintained fixation at the center of the display. At the end of the delay, a choice array containing two stimuli at random locations was presented and the animal was rewarded from making a saccadic eye movement to the stimulus that matched the cue (target). The presentation periods for the cue and array are indicated by horizontal bars. The cues were chosen for each cell such that one would activate a cell when presented alone (“good” cue) and one would only poorly activate the cell when presented alone (“poor” cue). Responses to identical choice arrays are shown separately for trials with the good versus poor stimulus for the recorded cells used as the cue. When the good cue was used, activity was higher during the delay period, and responses to the choice array remained high. When the poor cue was used, activity was lower during the delay period, and responses to the identical choice array were suppressed approximately 200 ms after the onset of the array. Thus, only cells selective for the target stimulus remained active, all other cells being suppressed. The saccadic eye movement to the target (asterisk) began about 300 ms after the onset of the array, well after responses to the nontarget stimuli were suppressed. (Adapted from refs. and .)

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References

    1. Desimone R. Science. 1992;258:245–246. - PubMed
    1. Desimone R, Ungerleider L G. In: Neural Mechanisms of Visual Processing in Monkeys. Boller F, Grafman J, editors. Vol. 14. New York: Elsevier; 1989. pp. 267–299.
    1. Ungerleider L G, Mishkin M. In: Two Cortical Visual Systems. Ingle D, Goodale M A, Mansfield R J W, editors. Cambridge, MA: MIT Press; 1982. pp. 549–586.
    1. Ungerleider L G, Haxby J V. Curr Opin Neurobiol. 1994;4:157–165. - PubMed
    1. Desimone R, Albright T D, Gross C G, Bruce C. J Neurosci. 1984;4:2051–2062. - PMC - PubMed

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