Anterior thalamic nuclei, but not retrosplenial cortex, lesions abolish latent inhibition in rats.

Abstract

The present study examined the effects of excitotoxic lesions in 2 closely related structures, the anterior thalamic nuclei and the retrosplenial cortex, on latent inhibition. Latent inhibition occurs when nonreinforced preexposure to a stimulus retards the subsequent acquisition of conditioned responding to that stimulus. Latent inhibition was assessed in a within-subject procedure with auditory stimuli and food reinforcement. As expected, sham-operated animals were slower to acquire conditioned responding to a stimulus that had previously been experienced without consequence, relative to a non-preexposed stimulus. This latent inhibition effect was absent in rats with excitotoxic lesions in the anterior thalamic nuclei, as these animals conditioned to both stimuli at equivalent rates. The retrosplenial lesions appeared to spare latent inhibition, as these animals displayed a robust stimulus preexposure effect. The demonstration here that anterior thalamic nuclei lesions abolish latent inhibition is consistent with emerging evidence of the importance of these thalamic nuclei for attentional control.

Thalamocortical interactions in cognition and disease: The mediodorsal and anterior thalamic nuclei

“…The ATN is also required for the processing of contextual memories (Carvalho-Netto et al, 2010;Marchand et al 2014;Law and Smith, 2012) with the ATN particularly important for recent, but not remote contextual fear memory retrieval (Lopez et al, 2018). Damage to the ATN also disrupts the ability of rats to form an attentional set during the attentional setshifting task (Wright, et al, 2015) and abolishes latent inhibition (Nelson et al, 2018).…”

The orbitofrontal cortex is necessary for learning to ignore

“…We tested whether the orbitofrontal cortex (OFC) is involved in learning to ignore specific cues by using a high-potency chemogenetic approach to selectively inactivate OFC principal neurons in rats during the pre-exposure phase of a within-subjects latent inhibition task. [5][6][7] The OFC has been proposed to be important for inferring hidden states, i.e., task states not explicitly signaled by ''real-world'' events. 4 Learning that a cue does not predict rewards when it was never explicitly paired with a reward beforehand, as happens during pre-exposure in latent inhibition, is a canonical example of hidden-state inference.…”

“…We used a within-subject controlled appetitive latent inhibition task structure inspired by previous studies. [5][6][7] The main procedure consisted of three phases:…”

Anterior thalamic nuclei: A critical substrate for non-spatial paired-associate memory in rats

“…ATN dysfunction slows rats’ ability to form an attentional set when learning a series of different non-spatial stimuli pairings in which only one stimulus dimension is rewarded (Wright et al, 2015; Bubb et al, 2021; Nelson, 2021). Latent inhibition associated with prior exposure to non-reinforced auditory cues is also impaired (Nelson et al, 2018). Conversely, relational processing of nonspatial stimuli during sensory preconditioning is unimpaired by ATN lesions (Ward-Robinson et al, 2002).…”