Neural Representation of Odor-Guided Behavior in the Rat Olfactory Thalamus

Abstract

The mediodorsal thalamus (MDT) is a higher-order corticocortical thalamic nucleus involved in cognition and memory. However, anatomically, the MDT is also the primary site of olfactory representation in the thalamus, receiving strong inputs from olfactory cortex and having reciprocal connections with orbitofrontal cortex (OFC). Nonetheless, its role in olfaction remains unclear. Here, we recorded single units in the MDT, as well as local field potentials in the MDT, piriform cortex (PCX), and OFC in rats performing a two-alternative odor discrimination task. We show that subsets of MDT units display odorant selectivity during sampling, as well as encoding of spatio-motor aspects of the task. Furthermore, the olfactory trans-thalamic network rapidly switches functional connectivity between MDT and cortical areas depending on current task demands, with, for example, MDT-PCX coupling enhanced during odor sampling and MDT-OFC coupling enhanced during the decision/goal approach compared with baseline and presampling. These results demonstrate MDT representation of diverse sensorimotor components of an olfactory task.

Central thalamic inactivation impairs the expression of action‐ and outcome‐related responses of medial prefrontal cortex neurons in the rat

“…The effects of MD lesions on associative learning and decision‐making are indicative of a critical role of these nuclei in prefrontal‐dependent, reinforcement‐guided responding (Bradfield et al., ; Browning, Chakraborty, & Mitchell, ; Corbit et al., ; Mitchell, ). Electrophysiological studies have shown that MD neurons represent information about task‐relevant stimuli, actions, and outcomes during different goal‐directed behaviors (Courtiol & Wilson, ; Han et al., ; Oyoshi et al., ; Tanibuchi & Goldman‐Rakic, ) and are closely coupled with PFC activity in animals engaged in adaptive decision‐making (Bolkan et al., ; Parnaudeau et al., , ). MD neurons exhibit activity related to lever press actions, movements between levers, and reinforcement events that closely match the timing of comparable responses observed in the mPFC in rats performing dDNMTP (Miller et al., ).…”

“…These results suggest an important role for the central thalamus in reinforcement‐guided responding that extends beyond working memory. Electrophysiological recordings have confirmed that neurons in MD and IL represent information about task‐relevant stimuli, actions, and outcomes unrelated to memory demands of goal‐directed behaviors (Costello, Zhu, May, Salinas, & Stanford, ; Courtiol & Wilson, ; Han, Lee, Kim, & Jung, ; Matsumoto, Minamimoto, Graybiel, & Kimura, ; Miller, Francoeur, Gibson, & Mair, ; Minamimoto, Hori, & Kimura, ; Oyoshi, Nishio, Asakura, & Ono, ; Tanaka & Kunimatsu, ; Wyder, Massoglia, & Stanford, ).…”

Adverse caregiving in infancy blunts neural processing of the mother: Translating across species

“…3A; X 2 (1,21)=3.834, p=0.05; relative risk=2.867)]. Specifically, infants with fewer risk factors were more likely to show secure, organized attachment, such as approaching the parent and being calmed by the parent's return whereas infants with more risk factors were more likely to exhibit disorganized attachment behaviors [X 2 (1,21)=14.32, p=0.0002, relative risk=5.5], such as initial greeting followed by avoidance or crying at a distance from the mother. Parents from the highrisk group were less sensitive to their infants than low-risk parents (r = -0.42, p = 0.008), and more sensitive parenting was associated with fewer disorganized behaviors than less sensitive parenting (r =-.44, p = 0.047) ( Fig.…”

“…Theta-gamma coupling, or modulation of gamma oscillations by theta events, is sensitive to developmental events 5,26,73,74 , has been associated with information processing 21,26,75 , and abnormal coupling is diagnostic of neuropsychiatric disorders 76 . Unexpectedly, we observed that adversity-reared pups exhibit more reliable theta-gamma coupling during SSP reunion with the mother than control pups.…”

The Olfactory Mosaic: Bringing an Olfactory Network Together for Odor Perception

“…The changes of coupling within the olfactory trans-thalamic pathway were also observed at the single trial level. We recorded mediodorsal thalamic single-units and LFPs in PCX and orbitofrontal cortex in rats performing a two-alternative odor choice discrimination task [(Courtiol & Wilson, 2016); Fig. 1].…”