A hard-wired priority map in the superior colliculus shaped by asymmetric inhibitory circuitry

Abstract

Bayguinov PO, Ghitani N, Jackson MB, Basso MA. A hardwired priority map in the superior colliculus shaped by asymmetric inhibitory circuitry. J Neurophysiol 114: 662-676, 2015. First published May 20, 2015 doi:10.1152/jn.00144.2015.-The mammalian superior colliculus (SC) is a laminar midbrain structure that translates visual signals into commands to shift the focus of attention and gaze. The SC plays an integral role in selecting targets and ultimately generating rapid eye movements to those targets. In all mammals studied to date, neurons in the SC are arranged topographically such that the location of visual stimuli and the endpoints of orienting movements form organized maps in superficial and deeper layers, respectively. The organization of these maps is thought to underlie attentional priority by assessing which regions of the visual field contain behaviorally relevant information. Using voltage imaging and patch-clamp recordings in parasagittal SC slices from the rat, we found the synaptic circuitry of the visuosensory map in the SC imposes a strong bias. Voltage imaging of responses to electrical stimulation revealed more spread in the caudal direction than the rostral direction. Pharmacological experiments demonstrated that this asymmetry arises from GABA A receptor activation rostral to the site of stimulation. Patch-clamp recordings confirmed this rostrally directed inhibitory circuit and showed that it is contained within the visuosensory layers of the SC. Stimulation of two sites showed that initial stimulation of a caudal site can take priority over subsequent stimulation of a rostral site. Taken together, our data indicate that the circuitry of the visuosensory SC is hard-wired to give higher priority to more peripheral targets, and this property is conferred by a uniquely structured, dedicated inhibitory circuit.

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“…Similarly, voltage imaging of rat brain slices has suggested a rostral–caudal asymmetry in sSC, in which excitation preferentially spreads caudally within sSC. Intriguingly, this effect is strongest when the activity flows up to sSC from dSC [97]. These results have strong implications on the role of local SC circuit properties for attention, salience and priority control.…”

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“…To bring our model in line with these results, whilst maintaining the eccentricity dependent activity in basal ganglia, we hypothesized that a “widening projection” exists between two maps in superior colliculus. As described in section 2.6, there is now experimental evidence for similar projections (Ghitani et al, 2014 ; Bayguinov et al, 2015 ) making this a plausible suggestion. Activities in one SC_deep layer remains eccentricity-dependent, with loops back to thalamus and cortex and through basal ganglia.…”

“…Although this pathway is a “wide” projecting field, the experiments do not indicate whether the projection widens along the rostral-caudal axis of the SC. Bayguinov et al ( 2015 ) present evidence for another projecting field within SC whose connectivity pattern does change along the rostral-caudal axis. This projection is inhibitory in nature.…”

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“…Finally, male brains are wired from front to back with a few inter-sphere connections and vice versa in the female leads to high-quality sensory motor speed accuracy in male and good face-social cognition in female [19].…”

“…All participants filled and signed a special brain sex matter questionnaire as yes or no , which included a set of special/specific and general questions and were scored ranging from 1-20 ,if YES was answered for 1,3,6 ,7,9,10, 11,14,15,17 the score was equal one point for each, while ; if YES answered for 2,4,5,8,12,13,16,18,19, 20 the score was equal to zero point for each , after totaling the scores 1score= very male brain sex , 20 scores =very female brain sex and between 1-20 scores =intermediate brain sex [7]. Then, use of calipers or ruler to measure digit length from middle of bottom creases to the top of the digit in cm, and measuring 2D:4D ratio which may be <1(short ratio) or >1(long ratio), also, this questionnaire correlates with index and ring digit lengths for both right and left hands (index finger shorter than ring finger indicates a male brain sex and vice versa).…”