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Understanding how the brain represents and processes complex, time-varying streams of sensory information

Dan Feldman and his team at UC Berkeley, members of the NSF-funded Temporal Dynamics of Learning Center, have made an important advance in understanding how the brain represents and processes complex, time-varying streams of sensory information. This issue is central for understanding how organisms recognize temporal patterns of sensory input, including in speech perception.

The researchers studied how the rodent brain represents touch information from the whiskers, which function similarly to human fingertips. Feldman and lab members Leah McGuire, Greg Telian and Keven Laboy-Juarez trained rats to discriminate temporal series of whisker deflections, and showed that rats guided their behavior by the time-averaged intensity of the whisker stimulus train, not by the precise timing or order of individual deflections. Thus, the brain temporally integrates tactile inputs for perception.

The team made neural recordings during behavior in primary somatosensory cortex, and found that neurons represented each individual whisker impulse on a rapid time scale, without signs of temporal integration. This indicates the primary sensory cortex primarily represents immediate sensory information, which must be integrated in higher cortical areas. Thus, these findings suggest a multi-step temporal integration process for sensory perception in cerebral cortex.

Leanne Chukoskie

Fig 1. Whisker stimuli and behavioral apparatus. (A) Schematic of training apparatus, showing the rat’s right whiskers resting on the moveable stimulus panel. (B) Panel kinematics for fast, medium, and slow impulses. Circles indicate maximum velocity. (C) Panel kinematics for FFF, FMS, SMF, and SSS sequences. Data for this panel are in S1 Data. (D) Mean speed, total duration, and first pulse peak velocity for the four sequences. SMF and FMS sequences had similar mean speed and duration (dashed lines).

This highlight summarizes the findings of the paper:
McGuire LM, Telian G, Laboy-Juárez KJ, Miyashita T, Lee DJ, Smith KA, Feldman DE (2016).  Short Time-Scale Sensory Coding in S1 during Discrimination of Whisker Vibrotactile Sequences.  PLoS Biol. 14(8): e1002549. doi: 10.1371/journal.pbio.1002549.