Responses In Association Cortex Research Articles

Influence of thalamic cooling on sensory responses in association cortex

O'BRIEN, J. H. AND S. M. ROSENBLUM. Influence of thalamic cooling on sensory responses in association cortex. BRAIN RES. BULL. 4(1) 91–98, 1979.—Evoked responses to light flash, click, and paw stimuli were recorded in the four cortical association areas in the acutely prepared cat. Average evoked responses (AEP) for 100 trials were formed before, during, and after localized cooling in the midline thalamus. Cooling of the midline thalamus reduced the magnitude of responses to click and paw stimuli, and increased or did not change the responses to light flash. There was very little similarity in trial-to-trial fluctuations of EP magnitude across cortical areas, and cooling did not reduce the similarity that existed. Waveform similarity was reduced by cooling for responses across the cortex to a single stimulus modality, whereas similarity of responses in a single cortical area to all three stimuli was not changed. The temporal components of the AEP influenced by thalamic cooling were different for different stimuli and cortical locations. It was concluded that the midline thalamo-cortical projection through the centromedian area to association cortices is particularly well-differentiated for multisensory responses in a single cortical region, and that the system should not be thought of as nonspecific but as convergent or multisensory.

Development of polysensory responses in association cortex of kitten.

Sensory responsiveness of single neurons in posterior association cortex of kittens that were 7 to 50 days old was investigated. The percentage of trimodal cells (that is, cells that respond to visual, auditory, and somesthetic stimulation) increased gradually until day 50, when percentages of trimodally responsive cells approached the adult level. In the youngest kittens, cells were predominantly responsive to only visual stimulation. With maturation, responsiveness to auditory and then to somesthetic stimulation was observed in increasing percentages of cells.

Comparison of evoked gross and unit responses in association cortex of waking cat

Averaged evoked gross and unit responses to auditory, visual and tactile stimuli were recorded from association cortex (posterior middle suprasylvian area) of the normal waking cat using a chronically implanted micro-manipulator system. Surface appearance and depth distribution of gross responses evoked by peripheral stimuli resembled such responses in the chloralosed preparation. There was a close and relatively invariant relationship between the gross response and the post-stimulus histogram of unit responses; the largest unit spikes tended to occur at or just beyond the peak of the depth negativity and smaller units tended to fire at the period of maximum negative slope of the gross depth potential. The data are interpreted as supporting the view that the gross evoked association response is generated in association cortex in the normal waking cat.

Organization of auditory, somatic sensory, and visual projection to association fields of cerebral cortex in the cat.

Organization of auditory, somatic sensory, and visual projection to association fields of cerebral cortex in the cat.