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Amphetamine elicits motoric changes by increasing the activity of central neurotransmitters such as dopamine and serotonin, but how these neurochemical signals are transduced into motor commands is unclear. The dorsolateral striatum (DLS), a component of the cortico-subcortical reentrant motor loop, contains abundant neurotransmitter transporters that amphetamine could affect. It has been hypothesized that DLS medium spiny neurons contribute to amphetamine's motor effects. To study striatal activity contributing to amphetamine-induced movements, activity of DLS neurons related to vertical head movement was recorded while tracking head movements before and after acute amphetamine injection. Relative to saline, all amphetamine doses induced head movements above pre-injection levels, revealing an inverted U-shaped dose-response function. Lower doses (1 mg/kg and 2 mg/kg, intraperitoneal) induced a greater number of long (distance and duration) movements than the high dose (4 mg/kg), which induced stereotypy. Firing rates (FR) of individual head movement neurons were compared before and after injection during similar head movements, defined by direction, distance, duration, and apex. Changes in FR induced by amphetamine were co-determined by dose and pre-injection FR of the neuron. Specifically, all doses increased the FRs of slower firing neurons but decreased the FRs of faster firing neurons. The magnitudes of elevation or reduction were greater at lower doses, but less pronounced at the high dose, forming an inverted U function. Modulation of DLS firing may interfere with sensorimotor processing. Furthermore, pervasive elevation of slow firing neurons' FRs may feed-forward and increase excitability in thalamocortical premotor areas, contributing to the increased movement initiation rate., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Long Evans rats (n=32) were trained for 2 weeks to respond to an auditory conditioned stimulus (CS) which signaled the delivery of a 20% sucrose unconditioned stimulus (US) with varying probabilities. Animals were randomly assigned to 1 of 4 groups. In the control groups, the CS signaled sucrose delivery with equal probabilities across two weeks, at 100% (Group 100-100) and 25% (Group 25-25) respectively. In the experimental groups (Group 100-25) and (Group 25-100), sucrose probabilities were switched between weeks 1 and 2. Three behavioral measures were recorded: latency to enter the sucrose port upon CS presentation, head entries throughout the session and ultrasonic vocalizations. The results suggest that all groups formed associations between the CS and US, as evidenced by a decrease in latency to respond to the CS across days. The experimental groups were also able to detect when sucrose probability changed, as evidenced by Group 25-100's increase in head entries, to the level of Group 100-100 in week 2, and Group 100-25's decrease in head entries, to the level of Group 25-25 in week 2. Group 100-25 also produced an increase in "22 kHz" ultrasonic vocalizations following the downshift on the first day of week 2. The increase in this ultrasonic frequency range, which is associated with negative affect in rats, preceded both the decrease in head entries and the increase in missed trials, consistent with a multistage model of behaviors resulting from US probability reduction., (Copyright © 2012 Elsevier B.V. All rights reserved.)

On April 24-27, 2010, the Motivational Neuronal Networks meeting took place in Wrightsville Beach, North Carolina. The conference was devoted to "Emerging, re-emerging, and forgotten brain areas" of the reward circuit. A central feature of the conference was four scholarly discussions of cutting-edge topics related to the conference's theme. These discussions form the basis of the present review, which summarizes areas of consensus and controversy, and serves as a roadmap for the next several years of research., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The rat dorsolateral striatum (DLS) has been implicated in habit formation. Previous studies in our laboratory found that as animals acquired a motor habit or remained goal-directed, tested by reward devaluation, the vast majority of DLS neurons decreased firing rates during the same responses over training days. However, mixed results have been reported in the literature regarding whether DLS neurons exhibit cue reactivity. In the present study, we reanalyzed a sample of DLS neurons in a task in which habitual behavior was acquired (dataset of Tang et al., 2007 [45]) and found that somatic sensorimotor as well as nonsomatomotor neurons of the DLS exhibited no cue-evoked firing. A second sample of DLS neurons related to licking in a task in which goal-directed behavior occurred (dataset of Tang et al., 2009 [46]) was also reanalyzed for cue-evoked correlates. Although behavior was cue guided, lick neurons did not exhibit cue-evoked firing. Given the complete absence of cue-related firing during habitual or goal-directed behavior, adaptations in DLS firing patterns may be regulated by movement-related learning rather than nonsomatosensory cues, consistent with convergent S1 and M1 afferents to the region. Striatal cue reactivity in the rat, is likely mediated within the dorsomedial and ventromedial striatum, in line with associative and limbic afferents to these regions, respectively., (Copyright 2010 Elsevier B.V. All rights reserved.)