scholarly journals Optimal Temporal Decoding of Neural Population Responses in a Reaction-Time Visual Detection Task

2008 ◽  
Vol 99 (3) ◽  
pp. 1366-1379 ◽  
Author(s):  
Yuzhi Chen ◽  
Wilson S. Geisler ◽  
Eyal Seidemann
Keyword(s):  
Reaction Time ◽  
Initial Response ◽  
Detection Task ◽  
Ideal Observer ◽  
Neural Population ◽  
Population Responses ◽  
Temporal Correlations ◽  
Lower Amplitude ◽  
Temporal Decorrelation ◽  
Speed And Accuracy

Behavioral performance in detection and discrimination tasks is likely to be limited by the quality and nature of the signals carried by populations of neurons in early sensory cortical areas. Here we used voltage-sensitive dye imaging (VSDI) to directly measure neural population responses in the primary visual cortex (V1) of monkeys performing a reaction-time detection task. Focusing on the temporal properties of the population responses, we found that V1 responses are consistent with a stimulus-evoked response with amplitude and latency that depend on target contrast and a stimulus-independent additive noise with long-lasting temporal correlations. The noise had much lower amplitude than the ongoing activity reported previously in anesthetized animals. To understand the implications of these properties for subsequent processing stages that mediate behavior, we derived the Bayesian ideal observer that specifies how to optimally use neural responses in reaction time tasks. Using the ideal observer analysis, we show that 1) the observed temporal correlations limit the performance benefit that can be attained by accumulating V1 responses over time, 2) a simple temporal decorrelation operation with time-lagged excitation and inhibition minimizes the detrimental effect of these correlations, 3) the neural information relevant for target detection is concentrated in the initial response following stimulus onset, and 4) a decoder that optimally uses V1 responses far outperforms the monkey in both speed and accuracy. Finally, we demonstrate that for our particular detection task, temporal decorrelation followed by an appropriate running integrator can approach the speed and accuracy of the optimal decoder.

scholarly journals Using a More Intuitive Cue in a Temporal Attention Discrimination Task to Compare Endogenous and Exogenous Mechanisms

2021 ◽  
Author(s):  
Colin R McCormick ◽  
Ralph S. Redden ◽  
Raymond M Klein
Keyword(s):  
Reaction Time ◽  
Discrimination Task ◽  
Detection Task ◽  
Temporal Attention ◽  
Cognitive Mechanism ◽  
Speed And Accuracy

Temporal attention is a cognitive mechanism that allows individuals to prepare to respond to ananticipated event. Lawrence and Klein (2013) distinguished two forms of temporal attention: oneelicited by purely endogenous alerting mechanisms, and one elicited through exogenous alertingmechanisms. Recently, McCormick et al. displayed that these mechanisms generate additiveeffects on reaction time, however more informative speed and accuracy comparisons were notpossible due to them being measured during a detection task. The current pair of experimentslooks to compare these two forms of temporal attention in a discrimination task while measuringboth speed and accuracy, by inducing methodological modifications that lower task demand.These manipulations were successful, as temporal cueing effects were observed for both thecombined form and the less-studied purely endogenous form. However, speed-accuracyperformance for these two forms of temporal attention did not align with our predictions basedon Lawrence and Klein (2013), leading us to speculate on the generalizability of their results.

scholarly journals Majority of choice-related variability in perceptual decisions is present in early sensory cortex

2017 ◽  
Author(s):  
Charles A. Michelson ◽  
Jonathan W. Pillow ◽  
Eyal Seidemann
Keyword(s):  
Visual Information ◽  
Visual Detection ◽  
Detection Task ◽  
Sensory Cortex ◽  
Neural Population ◽  
Processing Stage ◽  
Population Responses ◽  
Visible Target ◽  
Perceptual Variability ◽  
Neural Variability

ABSTRACTWhile performing challenging perceptual tasks such as detecting a barely visible target, our perceptual reports vary across presentations of identical stimuli. This perceptual variability is presumably caused by neural variability in our brains. How much of the neural variability that correlates with the perceptual variability is present in the primary visual cortex (V1), the first cortical processing stage of visual information? To address this question, we recorded neural population responses from V1 using voltage-sensitive dye imaging while monkeys performed a challenging reaction-time visual detection task. We found that V1 responses in the period leading to the decision correspond more closely to the monkey’s report than to the visual stimulus. These results, together with a simple computational model that allows one to quantify the captured choice-related variability, suggest that most this variability is present in V1, and that areas outside of V1 contain relatively little independent choice-related variability.

Semantic memory is both impaired and anomalous in schizophrenia

1994 ◽  
Vol 24 (1) ◽  
pp. 193-202 ◽  
Author(s):  
E. Y. H. Chen ◽  
A. J. Wilkins ◽  
P. J. McKenna
Keyword(s):  
Reaction Time ◽  
Semantic Memory ◽  
Reaction Time Task ◽  
Semantic Category ◽  
Semantic Relationship ◽  
Conceptual Category ◽  
Ambiguous Words ◽  
Schizophrenic Patients ◽  
Speed And Accuracy ◽  
Normal Controls

SynopsisThe integrity of semantic memory in schizophrenia was examined in a reaction time task requiring subjects to verify words as members or non-members of a conceptual category, where the words differed in their degree of semantic relationship to the category. Compared to matched normal controls, 28 schizophrenic patients were impaired on the task, showing slower responses in all conditions. In addition, their performance was anomalous in that they took longest to respond to items that were outside the category but semantically related to it, in contrast to the controls who took the longest to respond to ambiguous words at the borderline of the category. The pattern of ‘yes’ and ‘no’ responses of the patients was anomalous in a similar way. In both speed and accuracy of responding, the findings indicate that there is an outward shift of semantic category boundaries in schizophrenia.

Adaptation and Temporal Decorrelation by Single Neurons in the Primary Visual Cortex

2003 ◽  
Vol 89 (6) ◽  
pp. 3279-3293 ◽  
Author(s):  
Xiao-Jing Wang ◽  
Yinghui Liu ◽  
Maria V. Sanchez-Vives ◽  
David A. McCormick
Keyword(s):  
Cortical Neurons ◽  
Neural Coding ◽  
Model Neuron ◽  
Ionic Currents ◽  
Cellular Mechanism ◽  
Membrane Properties ◽  
Sensory Inputs ◽  
V1 Neurons ◽  
Temporal Correlations ◽  
Temporal Decorrelation

Limiting redundancy in the real-world sensory inputs is of obvious benefit for efficient neural coding, but little is known about how this may be accomplished by biophysical neural mechanisms. One possible cellular mechanism is through adaptation to relatively constant inputs. Recent investigations in primary visual (V1) cortical neurons have demonstrated that adaptation to prolonged changes in stimulus contrast is mediated in part through intrinsic ionic currents, a Ca2+-activated K+ current ( IKCa) and especially a Na+-activated K+ current ( IKNa). The present study was designed to test the hypothesis that the activation of adaptation ionic currents may provide a cellular mechanism for temporal decorrelation in V1. A conductance-based neuron model was simulated, which included an IKCa and an IKNa. We show that the model neuron reproduces the adaptive behavior of V1 neurons in response to high contrast inputs. When the stimulus is stochastic with 1/ f 2 or 1/ f-type temporal correlations, these autocorrelations are greatly reduced in the output spike train of the model neuron. The IKCa is effective at reducing positive temporal correlations at approximately 100-ms time scale, while a slower adaptation mediated by IKNa is effective in reducing temporal correlations over the range of 1–20 s. Intracellular injection of stochastic currents into layer 2/3 and 4 (pyramidal and stellate) neurons in ferret primary visual cortical slices revealed neuronal responses that exhibited temporal decorrelation in similarity with the model. Enhancing the slow afterhyperpolarization resulted in a strengthening of the decorrelation effect. These results demonstrate the intrinsic membrane properties of neocortical neurons provide a mechanism for decorrelation of sensory inputs.

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