Dynamic cortical lateralization during olfactory discrimination learning

Abstract

Bilateral cortical circuits are not necessarily symmetrical. Asymmetry, or cerebral lateralization, allows functional specialization of bilateral brain regions and has been described in humans for such diverse functions as perception, memory and emotion. There is also evidence for asymmetry in the human olfactory system, although evidence in non-human animal models is lacking. In the present study, we took advantage of the known changes in olfactory cortical local field potentials that occur over the course of odour discrimination training to test for functional asymmetry in piriform cortical activity during learning. Both right and left piriform cortex local field potential activities were recorded. The results obtained demonstrate a robust interhemispheric asymmetry in anterior piriform cortex activity that emerges during specific stages of odour discrimination learning, with a transient bias toward the left hemisphere. This asymmetry is not apparent during error trials. Furthermore, functional connectivity (coherence) between the bilateral anterior piriform cortices is learning- and context-dependent. Steady-state interhemispheric anterior piriform cortex coherence is reduced during the initial stages of learning and then recovers as animals acquire competent performance. The decrease in coherence is seen relative to bilateral coherence expressed in the home cage, which remains stable across conditioning days. Similarly, transient, trial-related interhemispheric coherence increases with task competence. Taken together, the results demonstrate transient asymmetry in piriform cortical function during odour discrimination learning until mastery, suggesting that each piriform cortex may contribute something unique to odour memory.

Dynamics of sensorimotor cortex activation during absence and myoclonic seizures in a mouse model of juvenile myoclonic epilepsy

“…Our study showed that although SWDs were not lateralized to the left or right hemisphere, myoclonic seizures exhibited a greater fraction of spikes starting in the right S1 than the left. Our finding of myoclonic seizure lateralization onset to right S1 in Gabra1 +/A322D mice is consistent with previous reports showing EEG lateralization in human JME, rodent audiogenic seizures, and rodent sensory processing …”

“…Our finding of myoclonic seizure lateralization onset to right S1 in Gabra1 +/A322D mice is consistent with previous reports showing EEG lateralization in human JME, 27 rodent audiogenic seizures, 28,29 and rodent sensory processing. [30][31][32] In addition, we found that myoclonic seizures initiate more focally within the sensorimotor cortex than SWDs. The majority of spikes in myoclonic seizures were initially detected exclusively in S1 electrodes, whereas a substantial fraction of SWD spikes were detected in S1 electrodes and at least one M1 electrode.…”

C-tactile afferents: Cutaneous mediators of oxytocin release during affiliative tactile interactions?

“…Perhaps reflecting the importance of these brain regions for regulating maternal behaviour, such as recognition of pup vocalisations & scents (Cohen et al, 2015;Richter et al, 2005), gender differences in oxytocin receptor expression have been reported. For example, denser receptor expression was found in the piriform cortex in female compared to male mice .…”

Olfactory Laterality Is Valence-Dependent in Mice

“…Rats/Long Evans males anterior PC LEFT Enhanced beta frequency band oscillations during the first stages of odour discrimination learning Performance-and context-dependent asymmetry [16] Rats/Long Evans males anterior PC orbitofrontal cortex…”

“…When considering olfactory learning, a study in rats has shown a highly significant lateralisation of translocation of enzyme protein kinase C from the cytosol to the membrane in the left PC [15]. More recently, Cohen and colleagues [16] showed a transient interhemispheric asymmetry in the anterior PC oscillatory activity at the initial stages of an odour discrimination task. This asymmetry was mainly the result of an enhanced event-related oscillatory activity in the left than in the right anterior PC.…”