Activation of Specific Interneurons Improves V1 Feature Selectivity and Visual Perception
Seung-Hee Lee, Alex C. Kwan, Siyu Zhang, Victoria Phoumthipphavong, John G. Flannery, Sotiris C. Masmanidis, Hiroki Taniguchi, Z. Josh Huang, Edward S. Boyden, Karl Deisseroth, Yang Dan · 2012
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Evidence (3)
Selective Routing
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BIO
Optogenetic activation of PV+ interneurons gates cortical responses to sharpen orientation tuning, unlike SOM+/VIP+ activation or excitatory-cell silencing.
"To quantify orientation tuning and direction selectivity of each neuron, we fitted the firing rate as a function of orientation by the sum of two Gaussian functions with peaks 180° apart:"
Data analysis, p. 8
This methods description shows how tuning width (σ) and selectivity were quantified, enabling the demonstration that increasing PV+ inhibitory activity selectively narrows tuning—a form of gating/route control over sensory representations relevant to selective routing in consciousness accounts .
"We alternated between the blocks of trials (24 orientations per block) with and without laser stimulation."
Methods, p. 7
Interleaving laser on/off blocks establishes a causal test of how targeted inhibitory gating affects encoding, consistent with selective routing mechanisms in theories of conscious access .
Figures
Figure 2 (p. 14)
: PV+ activation narrows tuning width (σ), indicating inhibitory gating sharpens representations—a hallmark of selective routing relevant to conscious processing bottlenecks.
Limitations: Findings are from mouse V1 and rely on optogenetic over-activation, which may exceed physiological levels; some recordings may differ across awake vs anesthetized conditions; links to conscious access are inferential.
Causal Control
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BIO
Causal activation of PV+ interneurons increases behavioral discriminability (d′) during an orientation task.
"In each block, laser stimulation was applied in 50% of randomly selected trials, and d′ was analyzed separately for trials with and without laser stimulation."
Behavioral experiment, p. 10
Randomized laser on/off within blocks isolates the causal influence of PV+ activation on perceptual performance (d′), demonstrating intervention-driven changes in behavior relevant to causal control in consciousness studies .
Figures
Figure 4 (p. 17)
: Optogenetic PV+ activation causally improves discrimination across difficulty levels, linking circuit-level manipulation to changes in report-relevant behavior.
Limitations: Behavioral improvements reflect task performance and may not directly index conscious experience; manipulation occurs at early sensory cortex; generalization to other species and tasks is uncertain.
Representational Structure
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PV+ vs SOM+ activation differentially modulates neuronal FI curves (subtractive threshold shift vs divisive gain), altering orientation code structure.
"For the whole-cell recording experiments (Supplementary Fig. 6), laser stimulation began 200 ms before the onset of current injection and ended 800 ms after termination of the current step."
Methods, p. 7
This whole-cell protocol enabled measuring how PV+ versus SOM+ activation altered FI functions, revealing distinct subtractive vs divisive modulations that reshape the representational code—conceptually analogous to representational geometry adjustments in AI models .
Figures
Figure 3 (p. 16)
: PV+ activation primarily increases threshold (subtractive), whereas SOM+ reduces slope (divisive), demonstrating subtype-specific changes to the neural code’s input–output structure.
Limitations: FI-function differences are shown in mouse V1 and may not generalize across areas or species; linking these coding changes to subjective experience is indirect.