Cerebellum-like circuits in the fish’s electrosensory lobe use anti-Hebbian LTD to generate a representation of predictable electrosensory input arising from motor commands, and to cancel self-generated electrosensory input. Purkinje-like medium ganglion (MG) cells receive strong electrosensory input at their basal dendrites, and a self-movement related Dasatinib input (corollary discharge and proprioceptive information) via sparse, parallel fiber inputs on their apical dendrites.

Parallel fiber synapses exhibit anti-Hebbian LTD (Bell et al., 1997; Han et al., 2000). When a specific self-movement signal consistently precedes a spike-eliciting electrosensory input, those parallel fiber synapses weaken, thus http://www.selleckchem.com/products/Adriamycin.html generating a negative image of predicted electrosensory input in MG cell activation. This learned negative image summates with the total electrosensory input arriving at the basal dendrites,

so that predicted electrosensory signals are canceled, and MG cell spiking reflects only unexpected stimuli. The specific form of the anti-Hebbian LTD rule is consistent with this role: the narrow temporal window increases the accuracy of the negative image and is broader in species that lack precisely timed corollary discharge signals (Harvey-Girard et al., 2010). The temporal asymmetry causes only self-motion inputs that immediately precede electrosensory input to be weakened, thus emphasizing causal relationships. PAK6 A computational model of anti-Hebbian LTD predicts the formation of negative images as observed in vivo (Roberts and Bell, 2000). This same circuit and anti-Hebbian LTD rule exist in other species, including

in skates, where it cancels self-generated electrical signals associated with respiration during passive electrosensation. In mammals, a remarkably similar circuit exists in the dorsal cochlear nucleus, with anti-Hebbian LTD at parallel fiber synapses onto Purkinje-like cartwheel cells (Tzounopoulos et al., 2004). Function of this circuit is not well understood, but it may adaptively adjust for ear position during sound localization, or more speculatively may cancel self-generated auditory signals associated with chewing, respiration, or vocalization (Requarth and Sawtell, 2011). The insect mushroom body contains hundreds of thousands of Kenyon cells (KCs) and is critical for associative olfactory learning. KCs sparsely encode olfactory input and make strong, convergent synapses on GABAergic β-lobe neurons (β-LNs) that provide a major inhibitory output to higher brain centers. During odor presentation, KC inputs evoke β-LN spikes that are highly synchronous across neurons, which is thought to facilitate feedforward information flow through olfactory circuits. KC→β-LN synapses exhibit robust Hebbian STDP, which enforces synchronous bLN spiking.