Biomedical subjects

P M Gochin

Publications and source records attributed to P M Gochin.

7 recordsLinked to original sources

PubMed1992

Intrinsic signal optical imaging in the forepaw area of rat somatosensory cortex.

The responses of somatosensory cortex (S-I) to tactile stimulation of the forepaw were assessed by intrinsic signal optical imaging. The tips of digits two or five were alternately touched with mechanical tappers while video photographs were taken of S-I illuminated by an 800-nm light source. The resulting images showed two highlighted areas about 300 microns in diameter and 500 microns apart. Generation of these images required less than 1 hr. Electrode penetrations placed in the areas highlighted during stimulation provided multiunit recordings with receptive fields appropriate for the stimulated digit and not the other digit. Penetrations between the high-lighted areas yielded receptive fields on intervening digits. These results demonstrate that intrinsic signal optical images are obtainable in S-I and confirm the functional somatotopy previously reported using electrical recording. Furthermore, the short time required to produce the images and the obtainable spatial resolution suggest that optical recording could be employed for the study of cortical reorganization in this brain region.

Animals↗

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↗

PubMed1990

Dynamic temporal properties of effective connections in rat dorsal cochlear nucleus.

In a prior report we presented evidence that functionally connected dorsal cochlear nucleus (DCN) neurons in close proximity can show differing peristimulus time histograms (PSTHs) in response to the same stimulus. We wished to further investigate how interconnections between such neurons might participate in the PSTH patterns. Methodology has recently been developed which permits measurement of rapid changes in effective connectivity between neuron pairs: the normalized joint PSTH. Using this technique we have observed that rapid changes in effective connectivity do occur in the DCN. These observations demonstrate that the effects of one DCN neuron on another cannot necessarily be understood by sequential recordings from single units, even if anatomical connectivity can be established.

Acoustic Stimulation↗

PubMed1989

Coordinated activity of neuron pairs in anesthetized rat dorsal cochlear nucleus.

We have recorded from small groups of neurons in the dorsal cochlear nucleus of anesthetized rats in an effort to study neuronal interactions. Multi-unit recordings on each single electrode were sorted by waveform into spike trains from individual neurons using a principal components spike sorter. Pairs of such sorted spike trains were studied with cross-correlation analysis to detect excitatory and/or inhibitory interactions. In a few cases recordings were obtained from two electrodes simultaneously, thus allowing cross-correlation studies without the consequences of spike train waveform sorting. All neurons were characterized by their strongest response frequency (at a fixed sound pressure level) and peristimulus histogram responses to 55 ms tone bursts. Fifty-eight percent of the neuron pairs studied showed peaks in their cross-correlograms indicative of coordinated neural activity. Of these pairs, 86% showed peak configurations (i.e. correlograms with asymmetrically located peaks) consistent with the interpretation that one cell induced the other to discharge. The remaining correlograms contained symmetric peaks which were centrally located, possibly due to shared input to these neuron pairs. Latencies of asymmetric peaks in cross-correlograms were typically 2 ms; consequently, an intervening excitatory synapse may be involved. Similar results were obtained from at least one pair of neurons where each neuron was recorded by a separate electrode. Strongest response frequencies of each neuron pair, for which they could be determined, were within 0.17 log units. Peristimulus histograms from each neuron in these pairs revealed that it was common for adjacent cells to respond with differing time patterns under the same stimulus conditions. The variations in histogram patterns of interconnected neurons suggests some relatively complex integrative function for these circuits.

Acoustic Stimulation↗

PubMed1988

Dose dependent morphine-induced pupillary fluctuations in the rat: frequency analysis.

Pupillary fluctuation induced by s.c. injection of morphine sulfate was studied in the rat using an infrared video pupillometer. The frequency and amplitude of the induced fluctuations throughout 47 min after drug injection was quantified using fourier analysis. Pupil fluctuation frequency was for the most part less than 0.25 Hz. The frequency profile showed a systematic increase in fluctuation amplitude with decreasing frequency. Aside from this systematic increase, no other consistent frequency trend was observed. The maximum drug effect occurred at approximately 15 min postinjection and remained constant for the remaining 30 min of the experiment. When fluctuation amplitude for all frequencies was pooled, a statistically significant, dose-dependent increase in fluctuation was found, with a peak effect between 10 and 40 mg/kg. Using frequency analysis techniques, we have demonstrated that pupil fluctuation induced by s.c. morphine administration in the rat is, like the concomitant mydriasis, a dose-related phenomenon.

Animals↗

PubMed1987

Saccades to visual targets are uncompensated after cerebellar stimulation.

Electrical stimulation of the posterior vermis produces a saccadic perturbation of the eyes. If this stimulation occurs after presentation of a visual target but before a trained saccade is initiated, the ensuing movement misses the target by an amount approximating the perturbation (uncompensated). These observations differ from those obtained after stimulation of the superior colliculus or frontal eye fields which result in compensated saccades that land on target. It is suggested that vermal stimulation may be acting outside the pontine burst feedback system.

Animals↗