Cortical plasticity and memory.

M M Merzenich; K Sameshima

doi:10.1016/0959-4388(93)90209-h

Home/Archive/PubMed

PubMed · 8513231

Cortical plasticity and memory.

M M Merzenich·K Sameshima

View original source ↗Export metadata ↓

Abstract

The roles of extrinsically modulated, plastic Hebb-like synapses and dynamic cortical cell assemblies underlying cortical plasticity in learning and memory operations are described. From our understanding of the distributed form of representation of learned behaviors in somatosensory and auditory cortical fields, and given new findings about the nature and distribution of responses representing learned and remembered stimuli in the inferior temporal cortex, a hypothetical picture of the cortical engram representing learned behaviors and memories is posited.

Explore related subjects

Afferent Pathways Aging Animals Cerebral Cortex Denervation Humans Memory Neuronal Plasticity Synapses Journal Article Review

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

M M Merzenich, K Sameshima. 1993. Cortical plasticity and memory.. https://doi.org/10.1016/0959-4388(93)90209-h

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1997

Experimentally induced retinal projections to the ferret auditory thalamus: development of clustered eye-specific patterns in a novel target.

We have examined the relative role of afferents and targets in pattern formation using a novel preparation, in which retinal projections in ferrets are induced to innervate the medial geniculate nucleus (MGN). We find that retinal projections to the MGN are arranged in scattered clusters. Clusters arising from the ipsilateral eye are frequently adjacent to, but spatially segregated from, clusters arising from the contralateral eye. Both clustering and eye-specific segregation in the MGN arise as a refinement of initially diffuse and overlapped projections. The shape, size, and orientation of retinal terminal clusters in the MGN closely match those of relay cell dendrites arrayed within fibrodendritic laminae in the MGN. We conclude that specific aspects of a projection system are regulated by afferents and others by targets. Clustering of retinal projections within the MGN and eye-specific segregation involve progressive remodeling of retinal axon arbors, over a time period that closely parallels pattern formation by retinal afferents within their normal target, the lateral geniculate nucleus (LGN). Thus, afferent-driven mechanisms are implicated in these events. However, the termination zones are aligned within the normal cellular organization of the MGN, which does not differentiate into eye-specific cell layers similar to the LGN. Thus, target-driven mechanisms are implicated in lamina formation and cellular differentiation.

Afferent Pathways↗

PubMed1997

Selective roles for hippocampal, prefrontal cortical, and ventral striatal circuits in radial-arm maze tasks with or without a delay.

The hippocampus, the prefrontal cortex, and the ventral striatum form interconnected neural circuits that may underlie aspects of spatial cognition and memory. In the present series of experiments, we investigated functional interactions between these areas in rats during the performance of delayed and nondelayed spatially cued radial-arm maze tasks. The two-phase delayed task consisted of a training phase that provided rats with information about where food would be located on the maze 30 min later during a test phase. The single-phase nondelayed task was identical to the test phase of the delayed task, but in the absence of a training phase rats lacked previous knowledge of the location of food on the maze. Transient inactivation of the ventral CA1/subiculum (vSub) by a bilateral injection of lidocaine disrupted performance on both tasks. Lidocaine injections into the vSub on one side of the brain and the prefrontal cortex on the other transiently disconnected these two brain regions and significantly impaired foraging during the delayed task but not the nondelayed task. Transient disconnections between the vSub and the nucleus accumbens produced the opposite effect, disrupting foraging during the nondelayed task but not during the delayed task. These data suggest that serial transmission of information between the vSub and the prefrontal cortex is required when trial-unique, short-term memory is used to guide prospective search behavior. In contrast, exploratory goal-directed locomotion in a novel situation not requiring previously acquired information about the location of food is dependent on serial transmission between the hippocampus and the nucleus accumbens. These results indicate that different aspects of spatially mediated behavior are subserved by separate, distributed limbic-cortical-striatal networks.

Afferent Pathways↗

PubMed1997

Blockade of afferent impulse activity disrupts on/off sublamination in the ferret lateral geniculate nucleus.

The ferret retinogeniculate projection is organized into on/off sublaminae within each eye-specific layer. The role of afferent activity in the formation of these sublaminae was examined. We report that when the activity of retinal ganglion cells is blocked with tetrodotoxin during postnatal weeks three and four, on/off sublamination is disrupted, supporting a role for afferent activity in the formation of this pattern.

Afferent Pathways↗