Papers by armando hernandez
Plastic and Reconstructive Surgery, 1967
Wolters Kluwer Health may email you for journal alerts and information, but is committed to maint... more Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining your privacy and will not share your personal information without your express consent. For more information, please refer to our Privacy Policy. ... Skip Navigation Links Home > October ...
Plastic and Reconstructive Surgery, 1967
Wolters Kluwer Health may email you for journal alerts and information, but is committed to maint... more Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining your privacy and will not share your personal information without your express consent. For more information, please refer to our Privacy Policy. ... Skip Navigation Links Home > October ...
Proceedings of The National Academy of Sciences, 2009
Monkeys have the capacity to accurately discriminate the difference between two acoustic flutter ... more Monkeys have the capacity to accurately discriminate the difference between two acoustic flutter stimuli. In this task, monkeys must compare information about the second stimulus to the memory trace of the first stimulus, and must postpone the decision report until a sensory cue triggers the beginning of the decision motor report. The neuronal processes associated with the different components of this task have been investigated in the primary auditory cortex (A1); but, A1 seems exclusively associated with the sensory and not with the working memory and decision components of this task. Here, we show that ventral premotor cortex (VPC) neurons reflect in their activities the current and remembered acoustic stimulus, their comparison, and the result of the animal's decision report. These results provide evidence that the neural dynamics of VPC is involved in the processing steps that link sensation and decision-making during auditory discrimination.
Proceedings of The National Academy of Sciences, 2011
The neuronal correlate of perceptual decision making has been extensively studied in the monkey s... more The neuronal correlate of perceptual decision making has been extensively studied in the monkey somatosensory system by using a vibrotactile discrimination task, showing that stimulus encoding, retention, and comparison are widely distributed across cortical areas. However, from a network perspective, it is not known what role oscillations play in this task. We recorded local field potentials (LFPs) from diverse cortical areas of the sensorimotor system while one monkey performed the vibrotactile discrimination task. Exclusively during stimulus presentation, a periodic response reflecting the stimulus frequency was observed in the somatosensory regions, suggesting that after initial processing, the frequency content of the stimulus is coded in some other way than entrainment. Interestingly, we found that oscillatory activity in the beta band reflected the dynamics of decision making in the monkey sensorimotor network. During the comparison and decision period, beta activity showed a categorical response that reflected the decision of the monkey and distinguished correct from incorrect responses. Importantly, this differential activity was absent in a control condition that involved the same stimulation and response but no decision making required, suggesting it does not merely reflect the maintenance of a motor plan. We conclude that beta band oscillations reflect the temporal and spatial dynamics of the accumulation and processing of evidence in the sensorimotor network leading to the decision outcome.
Philosophical Transactions of The Royal Society B: Biological Sciences, 2002
Journal of Neuroscience, 2010
We examined neural spike recordings from prefrontal cortex (PFC) while monkeys performed a delaye... more We examined neural spike recordings from prefrontal cortex (PFC) while monkeys performed a delayed somatosensory discrimination task. In general, PFC neurons displayed great heterogeneity in response to the task. That is, though individual cells spiked reliably in response to task variables from trial-to-trial, each cell had idiosyncratic combinations of response properties. Despite the great variety in response types, some general patterns held. We used linear regression analysis on the spike data to both display the full heterogeneity of the data and classify cells into categories. We compared different categories of cells and found little difference in their ability to carry information about task variables or their correlation to behavior. This suggests a distributed neural code for the task rather than a highly modularized one. Along this line, we compared the predictions of two theoretical models to the data. We found that cell types predicted by both models were not represented significantly in the population. Our study points to a different class of models that should embrace the inherent heterogeneity of the data, but should also account for the non-random features of the population.
Philosophical Transactions of The Royal Society B: Biological Sciences, 2002
In a typical sequential sensory discrimination task, subjects are required to make a decision bas... more In a typical sequential sensory discrimination task, subjects are required to make a decision based on comparing a sensory stimulus against the memory trace left by a previous stimulus. What is the neuronal substrate for such comparisons and the resulting decisions? This question was studied by recording neuronal responses in a variety of cortical areas of awake monkeys (Macaca mulatta), trained to carry out a vibrotactile sequential discrimination task. We describe methods to analyse responses obtained during the comparison and decision phases of the task, and describe the resulting findings from recordings in secondary somatosensory cortical area (S2). A subset of neurons in S2 become highly correlated with the monkey's decision in the task.
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Papers by armando hernandez