scholarly journals Signatures of vibration frequency tuning in human neocortex

2021 ◽  
Author(s):  
Lingyan Wang ◽  
Jeffrey M. Yau
Keyword(s):  
Vibration Frequency ◽  
Frequency Tuning ◽  
Perceptual Sensitivity ◽  
Fundamental Feature ◽  
Human Neocortex ◽  
Afferent System ◽  
Cortical Responses ◽  
Response Profile ◽  
Central Representation

Humans can perceive and discriminate vibration frequency, yet the central representation of this fundamental feature is unknown. Using fMRI, we discovered that cortical responses are tuned for vibration frequency. Voxel tuning was biased in a manner that reflects perceptual sensitivity and the response profile of the Pacinian afferent system. These results imply the existence of tuned populations that may encode naturalistic vibrations according to their constituent spectra.

Temporal-frequency tuning of direction selectivity in cat visual cortex

1992 ◽  
Vol 8 (4) ◽  
pp. 365-372 ◽  
Author(s):  
Alan B. Saul ◽  
Allen L. Humphrey
Keyword(s):  
Visual Cortex ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Direction Selectivity ◽  
Half Cycle ◽  
Low Frequencies ◽  
Preferred Direction ◽  
Cat Visual Cortex ◽  
Cortical Responses ◽  
Areas 17 And 18

AbstractResponses of 71 cells in areas 17 and 18 of the cat visual cortex were recorded extracellularly while stimulating with gratings drifting in each direction across the receptive field at a series of temporal frequencies. Direction selectivity was most prominent at temporal frequencies of 1–2 Hz. In about 20% of the total population, the response in the nonpreferred direction increased at temporal frequencies of around 4 Hz and direction selectivity was diminished or lost. In a few cells the preferred direction reversed.One consequence of this behavior was a tendency for the preferred direction to have lower optimal temporal frequencies than the nonpreferred direction. Across the population, the preferred direction was tuned almost an octave lower. In spite of this, temporal resolution was similar in the two directions. It appeared that responses in the nonpreferred direction were suppressed at low frequencies, then recovered at higher frequencies.This phenomenon might reflect the convergence in visual cortex of lagged and nonlagged inputs from the lateral geniculate nucleus. These afferents fire about a quarter-cycle apart (i.e. are in temporal quadrature) at low temporal frequencies, but their phase difference increases to a half-cycle by about 4 Hz. Such timing differences could underlie the prevalence of direction-selective cortical responses at 1 and 2 Hz and the loss of direction selectivity in many cells by 4 or 8 Hz.

scholarly journals Population Response Profiles in Early Visual Cortex Are Biased in Favor of More Valuable Stimuli

2010 ◽  
Vol 104 (1) ◽  
pp. 76-87 ◽  
Author(s):  
John T. Serences ◽  
Sameer Saproo
Keyword(s):  
Visual Cortex ◽  
Variable Interval ◽  
Population Response ◽  
Relative Value ◽  
Cortical Responses ◽  
Response Profile ◽  
Early Visual Cortex ◽  
Feature Based ◽  
Early Effects

Voluntary and stimulus-driven shifts of attention can modulate the representation of behaviorally relevant stimuli in early areas of visual cortex. In turn, attended items are processed faster and more accurately, facilitating the selection of appropriate behavioral responses. Information processing is also strongly influenced by past experience and recent studies indicate that the learned value of a stimulus can influence relatively late stages of decision making such as the process of selecting a motor response. However, the learned value of a stimulus can also influence the magnitude of cortical responses in early sensory areas such as V1 and S1. These early effects of stimulus value are presumed to improve the quality of sensory representations; however, the nature of these modulations is not clear. They could reflect nonspecific changes in response amplitude associated with changes in general arousal or they could reflect a bias in population responses so that high-value features are represented more robustly. To examine this issue, subjects performed a two-alternative forced choice paradigm with a variable-interval payoff schedule to dynamically manipulate the relative value of two stimuli defined by their orientation (one was rotated clockwise from vertical, the other counterclockwise). Activation levels in visual cortex were monitored using functional MRI and feature-selective voxel tuning functions while subjects performed the behavioral task. The results suggest that value not only modulates the relative amplitude of responses in early areas of human visual cortex, but also sharpens the response profile across the populations of feature-selective neurons that encode the critical stimulus feature (orientation). Moreover, changes in space- or feature-based attention cannot easily explain the results because representations of both the selected and the unselected stimuli underwent a similar feature-selective modulation. This sharpening in the population response profile could theoretically improve the probability of correctly discriminating high-value stimuli from low-value alternatives.

scholarly journals Cortical Resonance to Visible and Invisible Visual Rhythms

2020 ◽  
Vol 10 (1) ◽  
pp. 37 ◽  
Author(s):  
Claudio de’Sperati
Keyword(s):  
Video Clip ◽  
External World ◽  
Perceptual Sensitivity ◽  
Speed Modulation ◽  
Cortical Responses ◽  
Video Scene ◽  
Amplitude Increase ◽  
Adults And Children ◽  
The Right ◽  
Sensitivity Increase

Humans are rather poor in judging the right speed of video scenes. For example, a soccer match may be sped up so as to last only 80 min without observers noticing it. However, both adults and children seem to have a systematic, though often biased, notion of what should be the right speed of a given video scene. We therefore explored cortical responsiveness to video speed manipulations in search of possible differences between explicit and implicit speed processing. We applied sinusoidal speed modulations to a video clip depicting a naturalistic scene as well as a traditional laboratory visual stimulus (random dot kinematogram, RDK), and measured both perceptual sensitivity and cortical responses (steady-state visual evoked potentials, SSVEPs) to speed modulations. In five observers, we found a clear perceptual sensitivity increase and a moderate SSVEP amplitude increase with increasing speed modulation strength. Cortical responses were also found with weak, undetected speed modulations. These preliminary findings suggest that the cortex responds globally to periodic video speed modulations, even when observers do not notice them. This entrainment mechanism may be the basis of automatic resonance to the rhythms of the external world.

scholarly journals Investigation of layer specific BOLD in the human visual cortex during visual attention

2021 ◽  
Author(s):  
Tim van Mourik ◽  
Peter J. Koopmans ◽  
Lauren J. Bains ◽  
David G. Norris ◽  
Janneke F.M. Jehee
Keyword(s):  
Visual Cortex ◽  
Visual Stimulation ◽  
False Positive Rate ◽  
Stimulus Location ◽  
Bold Response ◽  
Cortical Responses ◽  
Response Profile ◽  
Positive Rate ◽  
The Individual ◽  
7T Fmri

AbstractDirecting spatial attention towards a particular stimulus location enhances cortical responses at corresponding regions in cortex. How attention modulates the laminar response profile within the attended region, however, remains unclear. In this paper, we use high field (7T) fMRI to investigate the effects of attention on laminar activity profiles in areas V1-V3; both when a stimulus was presented to the observer, and in the absence of visual stimulation. Replicating previous findings, we find robust increases in the overall BOLD response for attended regions in cortex, both with and without visual stimulation. When analyzing the BOLD response across the individual layers in visual cortex, we observed no evidence for laminar-specific differentiation with attention. We offer several potential explanations for these results, including theoretical, methodological and technical reasons. Additionally, we provide all data and pipelines openly, in order to promote analytic consistency across layer-specific studies, improve reproducibility, and decrease the false positive rate as a result of analytical flexibility.

A Realist Perspective on Contemporary "Economic Theory" (Foreword by O. Ananyin)

2006 ◽  
pp. 75-98 ◽  
Author(s):  
T. Lawson
Keyword(s):  
Economic Theory ◽  
Life Events ◽  
Alternative Model ◽  
Economic Life ◽  
Social Phenomenon ◽  
Methodological Issues ◽  
Neoclassical Theory ◽  
Fundamental Feature ◽  
Major Powers ◽  
Realist Perspective

The author elaborates on methodological issues of current tendencies in neoclassical theory and demonstrates the necessity of an alternative model of science, which he calls "realist". According to this perspective, constant and regular conjunctions of economic life events should not be the main object of analysis. Rather, the author proposes to consider structures and mechanisms governing events in question. Instead of deductivism, which, as Lawson believes, is a fundamental feature of orthodox economics, the abductive method of economic explanation is proposed that entails investigation of major powers, on which any social phenomenon depends. Society is thereby regarded not as a closed, but rather as an open system.

Spatial and Temporal Frequency Tuning of Motion-in-Depth Aftereffect

2008 ◽  
Vol 128 (7) ◽  
pp. 1015-1022
Author(s):  
Sheng Ge ◽  
Makoto Ichikawa ◽  
Atsushi Osa ◽  
Keiji Iramina ◽  
Hidetoshi Miike
Keyword(s):  
Frequency Tuning ◽  
Temporal Frequency ◽  
Motion In Depth
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