Assembly and use of new task rules in fronto-parietal cortex

Severe capacity limits, closely associated with fluid intelligence, arise in learning and use of new task rules. We used fMRI to investigate these limits in a series of multirule tasks involving different stimuli, rules, and response keys. Data were analyzed both during presentation of instructions and during later task execution. Between tasks, we manipulated the number of rules specified in task instructions, and within tasks, we manipulated the number of rules operative in each trial block. Replicating previous results, rule failures were strongly predicted by fluid intelligence and increased with the number of operative rules. In fMRI data, analyses of the instruction period showed that the bilateral inferior frontal sulcus, intraparietal sulcus, and presupplementary motor area were phasically active with presentation of each new rule. In a broader range of frontal and parietal regions, baseline activity gradually increased as successive rules were instructed. During task performance, we observed contrasting fronto-parietal patterns of sustained (block-related) and transient (trial-related) activity. Block, but not trial, activity showed effects of task complexity. We suggest that, as a new task is learned, a fronto-parietal representation of relevant rules and facts is assembled for future control of behavior. Capacity limits in learning and executing new rules, and their association with fluid intelligence, may be mediated by this load-sensitive fronto-parietal network

Personality traits and behavioral patterns associated with systolic blood pressure levels in college males

1. 1. Seventy-four young white male college students (out of an original pool of 800 examined) were selected for having high or low systolic readings taken on a registration line. These students were then classified according to their paired casual, usual, and sustained levels of systolic blood pressure. Of 21 persons with a high paired casual systolic blood pressure (two independent determinations in excess of 140 mm Hg), 16 were also characterized as belonging to a `usual high' group (blood pressure in excess of 131 mm on resting and repeated home readings). A `sustained' high blood pressure group (n = 11) was further obtained by selecting those who were `high' on their paired casual and their `usual' blood pressure levels. These blood pressure patterns were then related with self ratings on the Cattell 16 PF questionnaire.2. 2. A consistent elevation to the upper range of normal in the systolic blood pressure of these college males was associated with `submissiveness' and `sensitivity' as defined by Cattell's 16 PF questionnaire. Subjects with `high paired casual' systolic blood pressures described themselves as motivated to obtain social contacts, but in a `sensitive' and `anxious' manner.3. 3. Subjects who were later selected for having a single high systolic blood pressure reading taken on first entering the physician's office (their second casual reading) tended more frequently to yield in an argument and then afterwards to change their private opinions toward agreement with partners who had an initially low systolic reading.4. 4. Whereas obesity was highly correlated with higher systolic levels, the psychological correlates of obesity were different from those related to elevated `casual' or `sustained' blood pressure. Obese subjects in this population appeared to be physically active, and more confident, though somewhat anxious under the stress of school examinations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32127/1/0000180.pd

Same task rules, different responses:Goal neglect, stimulus-response mapping and response modalities

To complete complex tasks, individuals must actively maintain task rules to direct behavior correctly. Failure to use task rules appropriately, termed goal neglect, has been shown across both vocal and manual response modalities. However, previous goal maintenance studies have differed not only in the response modality that they require, but also in the complexity of the stimulus–response mappings that participants must use during the task. The present study examines the effects of both response modality and stimulus–response mapping complexity, separately, on the rate of goal neglect in a modification of a classic goal maintenance task. Seventy-two younger adults were administered a shape-monitoring task, with three between-subjects response conditions: a vocal response with a simple stimulus–response mapping, a vocal response with a complex stimulus–response mapping, and a manual response with a complex stimulus–response mapping. Contrasting the rate at which task rules were neglected between response conditions showed that participants using complex stimulus–response mappings committed more frequent goal neglect than those using simple mappings, but that participants using vocal or manual responses did not differ in their rate of goal neglect once both responses required complex mappings. This suggests that the need to represent novel and complex stimulus–response mappings, of any modality, at the same time as novel task rules within working memory leads to some task rules being insufficiently maintained

COMT val158met Genotype Affects Recruitment of Neural Mechanisms Supporting Fluid Intelligence

Fluid intelligence (gf) influences performance across many cognitive domains. It is affected by both genetic and environmental factors. Tasks tapping gf activate a network of brain regions including the lateral prefrontal cortex (LPFC), the presupplementary motor area/anterior cingulate cortex (pre-SMA/ACC), and the intraparietal sulcus (IPS). In line with the “intermediate phenotype” approach, we assessed effects of a polymorphism (val158met) in the catechol-O-methyltransferase (COMT) gene on activity within this network and on actual task performance during spatial and verbal gf tasks. COMT regulates catecholaminergic signaling in prefrontal cortex. The val158 allele is associated with higher COMT activity than the met158 allele. Twenty-two volunteers genotyped for the COMT val158met polymorphism completed high and low gf versions of spatial and verbal problem-solving tasks. Our results showed a positive effect of COMT val allele load upon the blood oxygen level–dependent response in LPFC, pre-SMA/ACC, and IPS during high gf versus low gf task performance in both spatial and verbal domains. These results indicate an influence of the COMT val158met polymorphism upon the neural circuitry supporting gf. The behavioral effects of val allele load differed inside and outside the scanner, consistent with contextual modulation of the relation between COMT val158met genotype and gf task performance