Representations in the Human Prefrontal Cortex

ABSTRACT— The prefrontal cortex (PFC) in humans has been studied for more than a century, but many crucial questions about its functions remain unanswered. This paper will highlight a few key differences between human and animal PFCs, and between the human PFC (HPFC) and other parts of the human brain. We then make a case that the HPFC is critically important for executing behaviors over time and integrating disparate information from throughout the brain. Finally, we will focus on our position in the current debate regarding how the HPFC performs its functions and discuss future directions for research.     

Testing the BOSS hypothesis: Evidence for position-insensitive orthographic priming in the lexical decision task

One recent conceptualization of the process of lexical access, the basic orthographic syllabic structure (BOSS) hypothesis, has been developed from a number of separate empirical and theoretical sources, and implicates distinct characteristics of the word recognition process. Using a lexical decision]priming paradigm, the present study tested all such characteristics simultaneously, together with a control condition in which simple sequences of letters were repeated within pairs of words, occupying different serial positions in each member of a pair. No evidence was obtained to suggest that BOSSs enjoy a special psychological status. Yet evidence from the same experiment suggests that words are processed via multiletter units in the lexical decision task, and that these units are not position specific, because they produce facilitation even when presented in different serial positions across primes and targets. Two interpretations of this position-insensitive orthographic priming are presented.     

Distress and performance appraisal satisfaction

120 quality assurance engineers indicated how frequently job stressors, causing distress related to role ambiguity, role conflict, role overload, and career development, affected them at work. They also indicated their satisfaction with their most recent performance appraisal. Satisfaction with performance appraisal was significantly negatively correlated with each stressor.     

Cue-producing behavior in the Capuchin monkey during reversal, extinction, acquisition, and overtraining

In a two-choice discrimination situation, a cue-producing response produced the discriminanda for 0.05 sec. The cue-producing responses beyond those normally necessary to identify the discriminanda thus provided only redundant information. Two of the four Capuchin monkeys studied showed a large increase in cue-producing responses during reversal learning and extinction, and they reversed much faster than the two whose cue-producing responses showed little increase. During acquisition of a difficult discrimination, the cue-producing responses of the first two subjects reached a high level and during overtraining gradually reduced to their initial low level. The results were related to Wyckoff's theory of observing behavior and to the notions of uncertainty, reduction, and lack of information as extensions of the concepts of reinforcement and motivation.     

Are preference reversals reduced when made explicit?

Previous research has shown that preferences for options, such as gambles, can reverse depending on the response mode. These preference reversals have been demonstrated when tasks were performed sequentially. That is, subjects completed one task before beginning another. In an attempt to eliminate preference reversals, we asked subjects to perform tasks simultaneously. That is, subjects made two types of responses for each pair of gambles before evaluating the next pair. In the condition with no financial incentives, preference reversal rates were slightly reduced. In another condition, subjects were paid for their participation and they were allowed to play a gamble with real monetary compensation. A gamble pair was randomly selected, and if a subject's responses in the two tasks were consistent for that pair, he or she was allowed to play the ‘preferred’ gamble. Otherwise, the experimenter selected the gamble from the pair. With these financial incentives, systematic preference reversals were eliminated for two of the three task combinations. Preference reversals continued to occur for attractiveness ratings versus selling prices, although, even for that pair of tasks, the reversal rate was significantly reduced. For all three task pairs, preference orders from the two tasks appeared to merge into more consistent orders.     

Suppression of optokinesis by a stabilized target: Effects of instruction and stimulus frequency

Subjects viewed a foveally stabilized target presented against a background field of dots moving sinusoidally. Several different modes of viewing the target were used (subjects were instructed to gaze, look, or hold), and the frequency of sinusoidal field motion was varied from 1/32 to 2 Hz. In line with previous findings, the presence of a stabilized target resulted in substantial suppression of optokinesis. The characteristics of this suppression (gain and phase of slow residual eye movements) were dependent on both the mode of viewing the target and the frequency of field motion. When subjects used an imaginary target, little suppression occurred. These findings provide an overall profile of dynamic characteristics of mechanisms involved in the suppression of optokinesis. They support the view that this suppression is significantly determined by the presence of a target against a moving background (even without retinal slip), and by the mode of attending to the target.