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Biomedical subjects

E K Miller

Publications and source records attributed to E K Miller.

5 recordsLinked to original sources
PubMed1991

A neural mechanism for working and recognition memory in inferior temporal cortex.

Inferior temporal (IT) cortex is critical for visual memory, but it is not known how IT neurons retain memories while new information is streaming into the visual system. Single neurons were therefore recorded from IT cortex of two rhesus monkeys performing tasks that required them to hold items in memory while concurrently viewing other items. The neuronal response to an incoming visual stimulus was attenuated if it matched a stimulus actively held in working memory, even when several other stimuli intervened. The neuronal response to novel stimuli declined as the stimuli became familiar to the animal. IT neurons appear to function as adaptive mnemonic "filters" that preferentially pass information about new, unexpected, or not recently seen stimuli.

Analysis of Variance↗
PubMed1991

Functional interactions among neurons in inferior temporal cortex of the awake macaque.

Functional interactions among inferior temporal cortex (IT) neurons were studied in the awake, fixating macaque monkey during the presentation of visual stimuli. Extracellular recordings were obtained simultaneously from several microelectrodes, and in many cases, spike trains from more than one neuron were extracted from each electrode by the use of spike shape sorting technology. Functional interactions between pairs of neurons were measured using cross-correlation. Discharge patterns of single neurons were evaluated using auto-correlation and PST histograms. Neurons recorded on the same electrode (within about 100 microns) had more similar stimulus selectivity and were more likely to show functional interactions than those recorded on different electrodes spaced about 250 to 500 microns apart. Most neurons tended to fire in bursts tens to hundreds of milliseconds in duration, and asynchronously from the stimulus induced rate changes. Correlated neuronal firing indicative of shared inputs and direct interactions was observed. Occurrence of shared input was significantly lower for neuron pairs recorded on different electrodes than for neurons recorded on the same electrode. Direct connections occurred about as often for neurons on different electrodes as for neurons on the same electrode. These results suggest that input projections are usually restricted to less than 500 micron patches and are then distributed over greater distances by intrinsic connections. Measurements of synaptic contribution suggest that typically more than 5 near-simultaneous inputs are required to cause an IT neuron to discharge.

Animals↗
PubMed1991

Habituation-like decrease in the responses of neurons in inferior temporal cortex of the macaque.

In both anesthetized and behaving macaques, we examined the responses of neurons in the inferior temporal cortex (IT) to repeated presentation of a visual stimulus. In anesthetized animals, the responsiveness of IT neurons decreased with repeated stimulus presentation at interstimulus intervals (ISIs) of 2-12 s but not at 20 s. Responsiveness recovered after a 5-min period of no stimulus presentation. The response decrement was similar in anesthetized and awake animals at a 2-s ISI, but at a 6-s ISI, response decrement in the awake animal was much less.

Anesthesia↗
PubMed1991

Expression of heat shock protein 70 and heat shock cognate 70 messenger RNAs in rat cortex and cerebellum after heat shock or amphetamine treatment.

The expression of strictly inducible hsp70 mRNAs and constitutively expressed hsc70 mRNAs was compared in cerebellum and cerebral cortex of control rats, heat-shocked rats, and rats made hyperthermic with amphetamine. An hsc70-specific oligonucleotide probe identified a 2.55-kb mRNA in cerebellum and cerebral cortex of all rats. An hsp70-specific oligonucleotide probe identified a 3.05-kb mRNA and a 3.53-kb mRNA in cerebellum and cerebral cortex of heat-shocked and amphetamine-treated rats, but not in control rats. Quantitation demonstrated that both hsp70 and hsc70 mRNA levels, relative to 18S rRNA levels, were increased following each treatment. The relative levels of both mRNAs were higher in cerebellum than in cerebral cortex. In amphetamine-treated rats, hsc70 mRNA relative levels increased at body temperatures greater than 39 degrees C, whereas hsp70 mRNA synthesis was induced at temperatures greater than 40 degrees C. Total thermal response values and relative levels of both mRNAs were compared. The results suggested that both the transcription and turnover of hsp70 mRNAs differed between cerebellum and cerebral cortex. At equivalent total thermal response values, amphetamine-treated rats had higher relative levels of hsp70 mRNAs than heat-shocked rats, suggesting that amphetamine enhanced the induction of hsp70 mRNAs.

Amphetamine↗