Texture Identification by Bounded Integration of Sensory Cortical Signals

• Published in: Current biology Vol. 29; no. 9; pp. 1425 - 1435.e5
• Main Authors: Zuo, Yanfang, Diamond, Mathew E.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 06-05-2019
• Subjects: Animals; Biomechanical Phenomena; bounded integration; decision making; evidence accumulation; Male; primary vibrissal somatosensory cortex; rat; Rats - physiology; Rats - psychology; Rats, Wistar; secondary vibrissal somatosensory cortex; texture discrimination; Touch - physiology; Touch Perception; vibrissa; Vibrissae - physiology; vS1; vS2; whisker; vibrissa; primary vibrissal somatosensory cortex; evidence accumulation; rat; vS2; vS1; whisker; texture discrimination; decision making; secondary vibrissal somatosensory cortex; bounded integration
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2019.03.017

Recent work demonstrated that when a rat palpates a surface to identify its texture, signals generated by whisker kinematics are integrated by the brain, one touch at a time, until the accumulated evidence supports a well-grounded choice. The framework of decision making through bounded integration, previously attributed to primates, thus extends to rodents. In the present study, we ask whether vibrissal somatosensory cortex (vS1 and vS2) functions as the integrator of incoming evidence or, alternatively, as a relay of evidence to a downstream integrator. Rats carried out 1–6 touches per trial to discriminate among candidate textures. We calculated the evidence for each texture, per touch, carried by the firing rates of sets of neurons in vS1 and vS2. The quantity of information within vS1 and vS2 did not grow progressively; instead, the decision was accounted for by modeling a downstream integrator that accumulated packets of vS1 and vS2 texture information until the total quantity of evidence for one texture reached a boundary. In this behavioral task, vibrissal somatosensory cortex appears to act as a sensory relay. Bounded integration is likely to take place in regions targeted by somatosensory cortex.
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•Rats identify textures by carrying out 1–6 vibrissal touches per trial•Somatosensory cortical firing encodes vibrissal kinematics one touch at a time•Somatosensory cortex relays packets of texture evidence to a downstream integrator•Choice is triggered when the evidence across touches is integrated to a boundary
When a rat palpates a surface to identify texture, vibrissal kinematic evidence is integrated by the brain one touch at a time. In this study, Zuo and Diamond find that vibrissal somatosensory cortex (vS1 and vS2) acts as a touch-by-touch distributor of evidence to a downstream integrator, where accumulation to a boundary triggers the decision.