Brain asymmetry improves processing of sensory information
Our brains are asymmetric but does this matter for effective cognitive function?
Elena Dreosti, Steve Wilson and colleagues think it does.
By imaging activity of individual neurons in larval zebrafish they found a region of the brain in which most neurons responding to a light stimulus were on the left whereas most responding to odour were on the right (Figure 1). In brains that were symmetric with either double-left or double-right character, they observed that responses to odour or to light were almost absent. These results show that loss of brain asymmetry can have significant consequences upon sensory processing and circuit function and raises the possibility that defects in the establishment of brain lateralization could be causative of cognitive or other symptoms of brain dysfunction.
Figure 1. Examples of neuronal activity in the left and right habenular nuclei (L Hb and R Hb) of four different four-day old fish with normal left-right habenular laterality (LR), reversed laterality (RL), symmetric double-right (RR) and symmetric double-left (LL) habenulae showing lateralization of neuronal responses to light and odour. Neuronal cell bodies are shown as dots colour-coded in red, blue, violet, or white depending on whether they responded to light, odour, both light and odour, or were non-responding.
Original article: Dreosti E., Llopis, N., Carl M., Yaksi E. & Wilson S.W. (2013) Left-right asymmetry is required for the habenulae to respond to both visual and olfactory stimuli. Current Biology http://dx.doi.org/10.1016/j.cub.2014.01.016