Out of Context: NMDA Receptor Antagonism in the Avian 'Prefrontal Cortex' Impairs Context Processing in a Conditional Discrimination Task.

Processing of context information is implicated in prefrontal functions as response selection or attention. N-methyl-D-aspartate (NMDA) receptors in the mammalian prefrontal cortex (PFC) and in the nidopallium caudolaterale (NCL) of birds, the avian functional equivalent of the PFC, are involved in learning, which also requires processing of context. The authors investigated the role of NMDA receptors in the pigeon (Columba livia) NCL for context processing and response selection in a simultaneous-matching-to-sample task with 2 trial types, requiring either processing of context information, delivered by a conditional stimulus (context dependent), or only recall of a stimulus-response association (fixed response). The competitive NMDA antagonist DL-2-amino-5-phosphonovaleric acid impaired performance only in context-dependent trials. Therefore, NMDA receptors in the avian PFC participate in response selection requiring context processing rather than in response selection per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of acetylcholine in negative patterning in turtles (Chrysemys picta).

Turtles were run on a negative patterning task involving 2 positive elements, a key with white stripes on a black background, and a solid red key, and a compound stimulus combining the 2 elements, white stripes on a red background. Injections of scopolamine, methylscopolamine, or saline were started at the same time that the compound stimulus was introduced, after the animals had been autoshaped to press the key for each of the elements. Scopolamine disrupted the learning of negative patterning, but methylscopolamine had no effect. In contrast, learning of a simple discrimination between the elements was not affected by scopolamine. These results show that muscarinic cholinergic receptors are involved in the learning of negative patterning in turtles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired learning of a color reversal task after NMDA receptor blockade in the pigeon (Columbia livia) associative forebrain (Neostriatum Caudolaterale).

The neostriatum caudolaterale (NCL) in the pigeon (Columba livia) forebrain is a multisensory associative area and a functional equivalent to the mammalian prefrontal cortex (PFC). To investigate the role of N-methyl-{D}-aspartate (NMDA) receptors in the NCL for learning flexibility, the authors trained pigeons in a color reversal task while locally blocking NMDA receptors with {D},{L}-2-2-amino-5phosphorrovalerate (AP-5). Controls received saline injections. AP-5-treated pigeons made significantly more errors and showed significantly stronger perseveration in a learning strategy applied by both groups but were unimpaired in initial learning. Results indicate that NMDA receptors in the NCL are necessary for efficient performance in this PFC-sensitive task, and that they are involved in extinction of obsolete information rather than in acquiring new information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anxious Responses to Predictable and Unpredictable Aversive Events.

Anxiety induced by 2 types of predictable and unpredictable aversive stimuli, an unpleasant shock or a less aversive airblast to the larynx, were investigated in a between-group design. Participants anticipated predictable (signaled) or unpredictable (not signaled) aversive events, or no aversive event. Unpredictable, relative to predictable, contexts potentiated the startle reflex in the shock group but not in the airblast group. These data suggest that unpredictability can lead to a sustained level of anxiety only when the pending stimulus is sufficiently aversive. Because predictable and unpredictable danger may induce different types of aversive responses, the proposed design can serve as a useful tool for studying the neurobiology and psychopharmacology of fear and anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensation Seeking and the Aversive Motivational System.

Sensation seeking (SS) has traditionally been viewed as a phenomenon of the appetitive motivational system. The limited SS research exploring contributions from the aversive motivational system reveals greater anxious reactivity to dangerous activities among low sensation seekers. The present study extends this line of work by comparing levels of fear and anxiety during anticipation of predictable and unpredictable aversive stimuli across high- and low-SS groups. Low sensation seekers displayed greater fear-potentiated startle (FPS) to predictable aversive stimuli, and only those low on SS showed FPS and skin conductance response effects during experimental contexts in which aversive stimuli were delivered unpredictably. Findings implicate enhanced apprehensive anticipation among those low on SS as a potential deterrent for their participation in intense and threatening stimulus events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)