Search PubMed⌕ Search

Biomedical subjects

C M Gray

Publications and source records attributed to C M Gray.

42 records · Page 3Linked to original sources
PubMed1986

Chemical dependencies of learning in the rabbit olfactory bulb: acquisition of the transient spatial pattern change depends on norepinephrine.

Intracerebral cannulas were implanted in both olfactory bulbs of 6 rabbits. A surface electrode-array (8 X 8) was implanted epidurally on the lateral surface of the left bulb. Each rabbit was conditioned to respond to sniffing to an odor paired with cutaneous shock while receiving continuous intrabulbar infusion of either vehicle or propranolol (100 microM at 1 microliter/hr) in vehicle. After two training sessions to the original odor, a response to a new odor was conditioned under the influence of the alternate infusate. Electroencephalographic (EEG) activity was sampled on inspirations before and during odor presentations. During vehicle infusion a transient alteration in the pattern of activity was acquired that occurred during the second and third inspirations following presentation of the reinforced odor. The acquisition did not occur when propranolol was infused. No significant pattern changes occurred with unreinforced odors in either condition. There was no local anesthetic effect of the racemic mixture of propranolol found for any type of electric activity, including antidromic spike activity observed in an independent control group. Intrabulbar norepinephrine injection (100 microM, 10 microL) resulted in an amplitude increase of the bulbar 40-80-Hz EEG and a potentiation of the transient spatial pattern change to a novel odor, when compared with those observed during vehicle infusion. It is concluded that norepinephrine released under centrifugal control may act to prevent or delay habituation that otherwise occurs rapidly to unreinforced odors.

Animals↗
PubMedDate not supplied

Heterogeneity in local distributions of orientation-selective neurons in the cat primary visual cortex.

We have employed the tetrode technique, which allows accurate discrimination of individual neuronal spike trains from multiunit recordings, in order to examine the variation of orientation selectivity among local groups of neurons. We recorded a total of 321 cells from 62 sites in area 17 of halothane-anesthetized cats; each site contained between three to ten neurons that were estimated to be less than 65 microns away from the tetrode tip. For each cell, we determined the orientation tuning in response to moving bars. Of the cells tested, 8.4% were unresponsive, 22.7% had no preferential response to any particular orientation, while 68.8% were tuned. The average difference in preferred orientation between cell pairs recorded at the same site was 10.7 deg, but the variance in preferred orientation differences differed significantly among sites. Some clusters of cells exhibited the same or nearly the same orientation preference, while others had orientation preferences that differed by as much as 90 deg. Our data demonstrate that the tuning for orientation is more heterogeneously distributed at a local level than previous studies have suggested.

Action Potentials↗