DS_Post_Fac

iModel

Supported by Wellcome Trust

DS_Post_Fac_T2
Direction Selective, Post-Synaptic, Facilatory,
Two Temporal Channels

Summary

This elaboration of the DS_Post_Fac model has two temporal channels, one fast and one slow. Each channel has separate LGN and V1 units up to the final direction selective (DS) stage. The DS cells are created from pair-wise interactions of spiking inputs in the fast channel, and separate pairwise interactions from the slow channel. This model displays adaptive temporal integration as defined by Bair and Movshon (2004; McLelland et al., in preparation). See the description of DS_Post_Fac for an explanation of the pairwise interaction.

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Results

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References

Baker PM, Bair W (2010) Cross-correlation analysis reveals circuits and mechanisms underlying direction selectivity. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00332
Bair W, Movshon JA (2004) Adaptive temporal integration of motion in direction-selective cells in macaque visual cortex. J Neurosci 24:7305--7323.
Baker PM, Bair W (in prep) Cross-correlation analysis reveals circuits and mechanisms underlying direction selectivity.
McLelland D, Baker PM, Bair W (in preparation) Channel-specific adaptive computation in macaque visual cortex.
Troyer TW, Krukowski AE, Priebe NJ, Miller KD (1998) Contrast-invariant orientation tuning in cat visual cortex: thalamocortical input tuning and correlation-based intracortical connectivity. J Neurosci 18:5908--5927.

(A) Organization of the four populations of spiking units in the slow channel: LGN-lateral geniculate nucleus, IN-inhibitory V1 simple cells, EX-excitatory V1 simple cells, DS-direction selective V1 cells. The populations for the fast channel (not shown) are LGN_M, IN_M, and EX_M.

(B) A population of four V1 DS complex cells.

(C) Within a 12,12,4 (x,y,z) lattice of V1 inhibitory simple cells (IN), cells in the 3rd z-layer that are presynaptic to the white-circled cell in (D) are shown in color. Colors indicate preferred orientation (see orientation key between panels C and D).

(D) The 12,12,4 lattice of V1 excitatory simple cells (EX) is shown where color indicates orientation (see orientation key). The white-circled cell gets IN inputs as marked in (C) and LGN inputs as marked in (E). The spatial LGN-driven excitatory RF is shown at the bottom of F (red square). This cell contribute input to the DS cell in (B, red-circle).

(E) The LGN lattice is 32,32,2, where the two z-layers represent ON and OFF cells. The 12,12,4 lattices of EX and IN cells align to the central 12,12 sub-grid of cells in the LGN, in terms of their RF centers within the field of view.

(F) Approximate spatial RFs for the four EX cells within the z-stack indicated by the white circle in (D). Note that the spatial phase of the RF shifts by 90 deg between z-layers.

(G) Each DS cell in (B) receives an excitatory conductance that is the sum of signals from subunits that operate on pairs of EX inputs. The RFs of the inputs pairs are approximately in quadrature (90 deg phase shift).

(H) The spike trains from one EX unit in a pair is convolved by a causal mask that peaks at DT 40 ms in the slow channel (DT 10 ms in the fast channel). The resulting mask signal, which delays and integrates the spikes from one unit, is then used to multiply the amplitude of the spikes from the second unit in the pair. The summed conductance of the post-synaptic DS unit (with spontaneous background inputs, i.e. noise, turned off for clarity), shows the influence of the EX spikes (red asterisks). Inputs from other subunits are marked with gray asterisks.