No abstract

To respond adaptively to change organisms must utilize information about recent events and environmental context to select actions that are likely to produce favorable outcomes. We developed a dynamic delayed nonmatching to position task to study the influence of spatial context on event-related activity of medial prefrontal cortex neurons during reinforcement-guided decision-making. We found neurons with responses related to preparation, movement, lever press responses, reinforcement, and memory delays. Combined event-related and video tracking analyses revealed variability in spatial tuning of neurons with similar event-related activity. While all correlated neurons exhibited spatial tuning broadly consistent with relevant task events, for instance reinforcement-related activity concentrated in locations where reinforcement was delivered, some had elevated activity in more specific locations, for instance reinforcement-related activity in one of several locations where reinforcement was delivered. Timing analyses revealed a limited set of distinct response types with activity time-locked to critical behavioral events that represent the temporal organization of dDNMTP trials. Our results suggest that reinforcement-guided decision-making emerges from discrete populations of medial prefrontal neurons that encode information related to planned or ongoing movements and actions and anticipated or actual action-outcomes in conjunction with information about spatial context.

Researchers investigating instrumental or operant conditioning in animals have constructed a wide variety of experimental equipment to arrange consequences for responding in controlled laboratory environments. Operant conditioning chambers, or "Skinner boxes," were devised so that experimenters could repeatedly deliver reinforcers following behavior without having to handle the animal trial after trial. An animal can activate one or more response devices inside the chamber, and the researcher can present reinforcement (e.g., food) or punishment (e.g., shock) to the animal inside the box, contingent on the response being made. The operant chamber has also been used to explore a broad range of issues in the stimulus control of behavior with what are called discriminated operants. Here, different discriminative stimuli, such as two differently colored pecking keys displaying white lines of two different orientations, are presented, and the animal is required to respond differently depending on the stimuli. These kinds of visual stimuli have been effectively used to examine such issues as associative competition (Reynolds, 1961), peak shift (Purtle, 1973), and memory (Blough, 1959) in animals.Although researchers investigating instrumental learning continue to rely heavily on the "traditional" Skinner box for experimentation, improvements in a number of technologies have considerably broadened the types of studies that can be conducted with the operant chamber. As well, over the past 3 decades, the nature of the stimulus information that experimenters have presented to animals in the operant chamber has become increasingly complex, due to advances in technology and to the expanding of researchers' interests to include issues related to animal perception and cognition (Fetterman, 1996;Wasserman, 1993).So, although traditional operant chambers continue to be useful, the stimulus information that is presented and the responses that are required of animals are becoming increasingly complex. Researchers of today and tomorrow will need a tool that is (1) powerful enough to probe sensitively into the perceptual and cognitive processes of animals, (2) inexpensive, so that many scientists can use the device, (3) flexible, so that it can be used to investigate a large variety of perceptual and cognitive issues, and (4) easy to construct and to use. Here, we report recent work whose aim was to develop an operant chamber that meets these criteria and that incorporates recent advances in computer technology. We hope that this report might be helpful both to beginning researchers in animal learning and behavior, who may be establishing an operant laboratory, and to more established researchers contemplating an update of their current operant technology. OverviewThe operant system consisted of five Apple eMac computers and four operant chambers, along with supporting hardware and software. Four of the eMac computers independently controlled the experimental sessions in each of the four operant chambers (Figure 1). The fifth eMac s...

The authors trained pigeons to discriminate images of human faces that displayed: (a) a happy or a neutral expression or (b) a man or a woman. After training the pigeons, the authors used a new procedure called Bubbles to pinpoint the features of the faces that were used to make these discriminations. Bubbles revealed that the features used to discriminate happy from neutral faces were different from those used to discriminate male from female faces. Furthermore, the features that pigeons used to make each of these discriminations overlapped those used by human observers in a companion study (F. Gosselin & P.G. Schyns, 2001). These results show that the Bubbles technique can be effectively applied to nonhuman animals to isolate the functional features of complex visual stimuli.

Summary Head-direction (HD) cells fire as a function of an animal’s directional heading in the horizontal plane during 2-D navigational tasks [1]. The information from HD cells is used with place and grid cells to form a spatial representation (cognitive map) of the environment [2,3]. Previous studies have shown that when rats are inverted (upside-down), they have difficulty learning a task that requires them to find an escape hole from one of four entry points, but can learn it when released from one or two start points [4]. Previous reports also indicate that the HD signal is disrupted when a rat is oriented upside-down [5,6]. Here we monitored HD cell activity in the two entry-point version of the inverted task and when the rats were released from a novel start point. We found that despite the absence of direction-specific firing in HD cells when inverted, rats could successfully navigate to the escape hole when released from one of two familiar locations by using a habit-associated directional strategy. In the continued absence of normal HD cell activity, inverted rats failed to find the escape hole when started from a novel release point. The results suggest that the HD signal is critical for accurate navigation in situations that require an allocentric cognitive mapping strategy, but not for situations that utilize habit-like associative spatial learning.