Research Highlights: In Brief...

Integration of stimuli from across the primate hand

JL Reed, P Pouget, HX Qi, Z Zhou, MR Bernard, MJ Burish, J Haitas, AB Bonds and JH Kaas (2008). Widespread spatial integration in primary somatosensory cortex. PNAS USA. 105 (29): 10233-10237.

Tactile sensation and discrimination are critical functions of the primate hand, yet the integration of signals from the many sensory neurons in the hand is not well understood.  Here, the authors provided evidence for widespread sensory input integration in the brain of the owl monkey, Aotus trivirgatus.  While small minimal receptive fields in monkey primary somatosensory cortex area 3b are important for stimulus localization, the results in this study indicate that integration in area 3b can also span beyond these small receptive fields.  Information is integrated not only within digits, but across the hand in a type of global stimulus processing.

 

Addiction, extinction and not the α2-adrenergic receptor

AR Davis, AD Shields, JL Brigman, M Norcross, ZA McElligott, A Holmes and DG Winder (2008). Yohimbine impairs extinction of cocaine-conditioned place preference in an α2-adrenergic receptor independent process. Learning Memory. 15: 667-676.

Extinction of learned place preference and drug addiction is poorly understood.  In this study, the authors investigated the role of the α2-adrenergic receptor (α2-AR) in extinction of cocaine-conditioned place preference (CPP) using the α2-AR antagonist yohimbine in behavioral and electrophysiological tests.  The authors reported that yohimbine impaired cocaine CPP similarly in α2-AR knockout mice and wildtype mice.  Because these effects of yohimbine, a relatively dirty drug, were not seen with a more selective α2-AR antagonist, atipamezole, and because yohimbine produced an electrophysiological depression of glutamatergic signaling in the bed nucleus of the stria terminalis that was also not seen with atipamezole, the authors suggest that the effects of yohimbine on cocaine CPP are independent of α2-AR.

 

Getting the Dopamine Rush

DH Zald, RL Cowan, P Riccardi, RM Baldwin, MS Ansari, R Li, ES Shelby, CE Smith, M McHugo and RM Kessler (2008). Midbrain Dopamine Receptor Availability Is Inversely Associated with Novelty-Seeking Traits in Humans. J. Neurosci. 28 (53): 14372-14378.

Novelty-seeking behaviors are a great predictor for tendency towards drug abuse in that both novelty-seeking and addiction involve dopamine stimulation of reward centers in the brain.  In this study, the authors correlated D2-like (D2 and D3) dopamine autoreceptor availability in the midbrain of human subjects using [18F]fallypride, a specific radiolabeled agonist.  Human subjects were given a novelty-seeking questionnaire, and then scanned using positron emission tomography.  The authors found an inverse relationship between D2-like receptor availability in the midbrain of subjects and their tendency towards novelty-seeking behavior, leading the authors to speculate that novelty-seekers may be self-medicating by causing the release of dopamine in response to thrills and novel environments.