Receptive field analysis and orientation selectivity of postsynaptic potentials of simple cells in cat visual cortex.

Postsynaptic potentials (PSPs) were recorded from cat striate cortical cells by the whole-cell in vivo recording technique using patch-clamp electrodes. EPSPs and IPSPs evoked by flashing bars on the receptive field at different positions and orientations revealed the spatial structure of the excitatory and inhibitory inputs. The elongation of the excitatory input field (length:width ratio) was found to be minimal (mean ratio of 1.

Excitation and inhibition in orientation selectivity of cat visual cortex neurons revealed by whole-cell recordings in vivo.

One striking transformation in response properties that occurs in the geniculo-cortical pathway is the appearance of a high degree of orientation selectivity in the cortex. This property may be conceived as arising purely from the excitatory inputs to the cell, as being structured largely by the inhibition a cortical cell receives or could be due to a combination of the two. We have studied the contributions of excitatory and inhibitory inputs to cortical cells' orientation selectivity by analyzing the postsynaptic potentials evoked in cat striate neurones by flashing stimuli of different orientations.

Functional comparison of neuronal properties in the primate posterior hippocampus and parahippocampus (area TF/TH) during different behavioural paradigms involving memory and selective attention.

Monkeys were trained on a delayed match-to-sample (DMS) task. In addition a standardized behavioural trial was performed which involved an experimenter approaching the animal in certain sequence and presenting edible or other objects ('raisin trial'). Neuronal activity of 617 units was recorded in the posterior parahippocampus (PH) and in the posterior hippocampus (H).

The neurophysiological correlates of colour induction, colour and brightness contrast.

Psychophysical experiments suggest that colour contrast and colour induction by surround lights can be explained as brightness contrasts (darkness induction) in the spectral region of the surround colour. It follows from this model that a chromatic surround reduces the gain of receptor-ganglion cell channels if the surround colour is in their excitatory spectral region. Thus, a green-sensitive cell (G+/R- or WS in our nomenclature) would respond less to a blue-green stimulus flashed into its receptive field when the surround (5 degrees/20 degrees inner/outer diameter) is illuminated with blue light.

Neurophysiological Correlates of Colour Induction on White Surfaces.

Coloured light surrounding a white surface of about equal luminance makes the white surface appear illuminated with an unsaturated light of the complementary colour. In an attempt to discover the neurophysiological basis of such colour induction, we recorded from spectrally opponent cells of the parvocellular layers of the lateral geniculate nucleus (P-LGN) of anaesthetized macaques. Only cells with wide-band (W) spectral sensitivity in the short (S) or long wavelength (L) part of the spectrum (WS, WL) are excited by white spots of light centred on their receptive field.