Academic journal article Attention, Perception and Psychophysics

News from the Field

Academic journal article Attention, Perception and Psychophysics

News from the Field

Article excerpt

Published online: 8 October 2013

# Psychonomic Society, Inc. 2013

VISUAL NEUROSCIENCE

Secondary cortex, second-order statistics

Freeman, J., Ziemba, C. M., Heeger, D. J., Simoncelli, E. P. & Movshon, J. A. (2013). A functional and perceptual signature of the second visual area in primates. Nature Neuroscience, 16 ,974--981.

Little patches of grating are typically used to model the preferred stimuli of neurons in primary visual cortex (V1). Freeman et al. address the question of what cells in secondary visual cortex (V2) prefer. Their technique in- volved simulating the response statistics (i.e. mean and variance) of neurons in primary visual cortex to pictures from nature; not portraiture or still lifes, but "textures" like honeycombs, sand on the beach, and stuff like that. When random visual stimuli were tweaked to produce the same statistics, Freeman et al. recorded healthy re- sponses from both V1 and V2. Then they further tweaked those stimuli, producing correlations (and other higher-order statistics) between model V1 neurons that matched those produced by natural textures. V1 neurones didn't respond any differently to these arguably even- more-natural stimuli, but V2 neurones sure did. Freeman et al. found a significant correlation between the higher- order statistics that V2 neurons like (e.g. correlations between the squared output from neurons sensitive to different spatial frequencies but the same region of space) and those that human observers can easily detect. (Neither neurones nor humans seem particularly sensitive to skewness or kurtosis.) Thus, it seems fair to say that "naturalistic texture" is the stuff V2 cells like. --J.A.S.

TIMING AND TIME PERCEPTION

You won't deceive a musician

Repp, B. H., Mendlowitz, H. B., & Hove, M. J. (2013) Does rapid auditory stimulation accelerate an internal Pacemaker? Don't bet on It. Timing and Time Perception , 1 ,65--76.

The literature on time perception reveals that an interval to- be timed is influenced by the context in which the interval is presented. For instance, tones are judged as longer when preceded by click trains than when preceded by silence. In contrast, the subjective duration of an interval preceded by a series of tone stimuli is shortened. These types of results are compatible with the idea that temporal judgments are based on the output of an 'internal pacemaker'-thus, external stimuli such as click trains alter the functioning of the pacemaker. Repp and collaborators tried to replicate these two lines of findings, using professional musicians as participants. Both replication attempts were unsuccessful. Although it is difficult to discard the possibility that some methodological differences might explain this failure to replicate, it remains likely that using highly trained musicians causes the difference. Because it is unlikely that normal participants use an internal pacemak- er for a temporal task and musicians don't, it is the pacemaker hypothesis that is questioned by the authors. One alternative explanation, however, might reside in the capability of musi- cians to ignore non relevant sounds.

One notable aspect of this paper is the fact that it is part of the first issue of a new journal dedicated to the study of psycho- logical time. Until 2013, there was no such specific journal for specialists (mostly experimental psychologists) studying the mechanisms involved in the field of timing and time perception. There is one now: Timing and Time Perception (http://www. brill.com/publications/journals/timing-time-perception). Interestingly, the first issue of this new journal is dedicated to Lorraine Allan, who passed away last December. Lorraine has dedicated the early years of her career to the study of time perception, being the co-editor, with the late John Gibbon, of Timing and Time Perception,publishedin1984bytheNew York Academy of Science. Lorraine also published several articles (including 7 in 1973 and 1974) on time perception in Perception & Psychophysics. …

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