Abstract: Research on the neural correlates of decision making in gambling tasks may be informative for understanding problem gambling. The present study explored confidence and overconfidence using magnetoencephalography (MEG) to measure brain activity during a judgment task. Nineteen undergraduates who self-identified as frequent gamblers (average age 19.7 years; 5 females, 14 males) participated in this study. Participants first completed the DIGS (Winters, Specker & Stinchfield, 2002), a measure of gambling pathology. They then engaged in a behavioral task of confidence assessment, wherein they answered two-alternative trivia questions and estimated the probability that each answer was correct. In a subsequent MEG task, they viewed the questions and a target answer, and indicated with a button press whether the target matched the correct answer. Confidence was directly related to activity in the right prefrontal cortex. Matching and mismatching targets were associated with activity in the medial occipital cortex and left supramarginal gyrus, respectively. An interaction of pathology and match/mismatch was observed in the right inferior occipital-temporal junction region, showing more activity following a mismatch in non-problem gamblers, but not in problem gamblers. Implications of the results for understanding of top-down modulation and attentional systems are discussed in relation to gambling behavior.

Abstract: Schizophrenia patients have difficulty distinguishing relevant from irrelevant auditory information. Auditory oddball paradigms are commonly used to investigate the processing of stimulus relevance. The present study used dense-array EEG and distributed source reconstructions to examine schizophrenia-normal differences in the processing of targets and standards as a function of the temporal sequence of stimuli. Brain responses were evaluated separately for early and late standards (standards 1-3 and 4-6 following a target, respectively) and early and late targets (those following 2-3 standards and 4-6 standards, respectively). The latencies of peaks (N1, P2, P3) in the event-related potential (ERP) waveforms did not differ between schizophrenia and normal subjects. However, schizophrenia-normal differences in neural activity, derived from minimum norm estimation, occurred at specific times during stimulus processing as a function of stimulus sequence. Schizophrenia patients displayed smaller activity than normals in early ERPs (left hemispheric N1, right frontal P2) to late targets, and they produced P3-like responses to late standards. Furthermore, during the P2/N2 time interval, opposite patterns of brain activity were elicited in schizophrenia and normal subjects in response to standards, indicating different neural responses to the same stimulus events. These results suggest attention allocation to task-irrelevant stimuli in schizophrenia, consequent upon insufficient representation of stimulus significance and context. Thus, schizophrenia compromises the ability to properly use context to solve even simple cognitive problems.

Abstract: The present study examined how increasing the rate of steady-state stimulation affects schizophrenia-normal differences on the N1 auditory-evoked potential, an index of auditory integration. Dense-array EEG was recorded while schizophrenia and normal subjects heard 1 kHz tones amplitude modulated at 10, 20, 40, or 80 Hz. Spectral power across frequency and time was calculated. The typically lower N1 amplitude in schizophrenia, observed at the 10 Hz burst rate, increased to nearly equal that of normal individuals at 20 Hz. Unlike normal subjects, schizophrenia subjects' power at N1 failed to increase at the 40 and 80 Hz burst rates. These results suggest steady-state stimuli, up to a point, provide the extra information needed for schizophrenia patients to more efficiently integrate auditory information.

Abstract: Four monkeys and 6 humans representing five different native languages were compared in the ability to categorize natural CV tokens of /b/ versus /d/ produced by 4 talkers of American English (2 male, 2 female) in four vowel contexts (/i, e, a, u/). A two-choice "left/right" procedure was used in which both percentage correct and response time data were compared between species. Both measures indicated striking context effects for monkeys, in that they performed better for the back vowels /a/ and /u/ than for the front vowels /i/ and /e/. Humans showed no context effects for the percentage correct measure, but their response times showed an enhancement for the /i/ vowel, in contrast with monkeys. Results suggest that monkey perception of place of articulation is more dependent than human perception on the direction of the F2 onset transitions of syllables, since back-vowel F2s differentiate /b/ and /d/ more distinctively. Although monkeys do not provide an accurate model of the adult human in place perception, they may be able to model the preverbal human infant before it learns a more speech-specific strategy of place information extraction.