Academic literature on the topic 'Neuronal discrimination'

Single cells were recorded from cortical area V4 of two rhesus monkeys (Macaca mulatta) trained on a visual discrimination task with two levels of difficulty. Behavioral evidence indicated that the monkeys' discriminative abilities improved when the task was made more difficult. Correspondingly, neuronal responses to stimuli became larger and more selective in the difficult task. A control experiment demonstrated that changes in general arousal could not account for the effects of task difficulty on neuronal responses. It is concluded that increasing the amount of attention directed toward a stimulus can enhance the responsiveness and selectivity of the neurons that process it.

We studied the effects of various patterns as contextual stimuli on human orientation discrimination, and on responses of neurons in V1 of alert monkeys. When a target line is presented along with various contextual stimuli (masks), human orientation discrimination is impaired. For most V1 neurons, responses elicited by a line in the receptive field (RF) center are suppressed by these contextual patterns. Orientation discrimination thresholds of human observers are elevated slightly when the target line is surrounded by orthogonal lines. For randomly oriented lines, thresholds are elevated further and even more so for lines parallel to the target. Correspondingly, responses of most V1 neurons to a line are suppressed. Although contextual lines inhibit the amplitude of orientation tuning functions of most V1 neurons, they do not systematically alter the tuning width. Elevation of human orientation discrimination thresholds decreases with increasing curvature of masking lines, so does the inhibition of V1 neuronal responses. A mask made of straight lines yields the strongest interference with human orientation discrimination and produces the strongest suppression of neuronal responses. Elevation of human orientation discrimination thresholds is highest when a mask covers only the immediate vicinity of the target line. Increasing the masking area results in less interference. On the contrary, suppression of neuronal responses in V1 increases with increasing mask size. Our data imply that contextual interference observed in human orientation discrimination is in part directly related to contextual inhibition of neuronal activity in V1. However, the finding that interference with orientation discrimination is weaker for larger masks suggests a figure-ground segregation process that is not located in V1.

We used the rat whisker touch as a model system to investigate the correlation between the response function of cortical neurons and the behavior of rats in a sensory detection versus discrimination task. The rat whisker–barrel system is structurally well characterized and represents one of the main channels through which rodents collect information about the environment. In experiment 1, we recorded neuronal activity ( n = 235) in the whisker area of the rat somatosensory cortex in anesthetized rats while applying vibrotactile stimuli of varying amplitudes to the whiskers. Neurons showed a characteristic sigmoidal input–output function, with an accelerating nonlinearity at low stimulus amplitudes and a compressive nonlinearity at high stimulus amplitudes. We further quantified the performance of individual neurons for stimulus detection and for discrimination across different stimulus pairs with identical amplitude differences. For near-threshold stimuli, the neuronal discrimination performance surpassed the detection performance despite the fact that detection and discrimination represented identical amplitude differences. This is consistent with the accelerating nonlinearity observed at low stimulus intensities. In the second stage of the experiment, four rats were trained to select the higher-amplitude stimulus between two vibrations applied to their whiskers. Similar to neuronal results, the rats' performance was better for the discrimination task compared with the detection task. The behavioral performance followed the same trend as that of the population of individual neurons. Both behavioral and neuronal data are consistent with the “pedestal effect” previously reported in human psychophysics.