Categorical and coordinate spatial task performance in inconsistent-handers versus consistent-right-handers: part II.

A previous study reported superior categorical and coordinate spatial task performance in inconsistent-versus consistent-right-handers (ICH versus CRH). Propper et al. used a three-dimensional (3D) computer-based task wherein individuals navigated to 21 locations within a realistic cityscape. During testing, participants were queried on their categorical and coordinate spatial knowledge of the map. In that study, the categorical and coordinate tasks may have inadvertently encouraged language coding of learned spatial information, potentially confounding spatial processing with recall ability for language-based information. Also, that study used a between-subjects design, which precludes examination of relationships between spatial knowledge as a function of handedness. The present study duplicated the learning task in Propper et al. using test stimuli that more faithfully represent spatial, and not language-based, information, as well as a within-subjects design. Results did not significantly replicate the previous study. Possible reasons for this finding are discussed.

Superior categorical and coordinate spatial task performance in inconsistent-handers relative to consistent-right-handers.

Categorical versus coordinate spatial tasks rely differentially on the left versus right hemisphere. Given the neuroanatomical and neurophysiological differences between inconsistent- versus consistent-right-handers (ICH versus CRH, respectively), such that the former demonstrates increased access to right hemisphere processes relative to the latter, it was hypothesized that ICH would outperform CRH on a test of coordinate spatial knowledge. Previous work demonstrating reliance on the right hemisphere for both categorical and coordinate information in non-right-handers using lateralized stimuli of brief duration suggested ICH might also outperform CRH on a categorical task as well. Participants navigated a virtual environment, landmark-to-landmark, within a 3-dimensional first-person point of view with high ecological validity, and then were tested on either their categorical or coordinate spatial knowledge. ICH were superior relative to the CRH on both types of spatial knowledge. Additionally, ICH navigated the environment during learning more quickly, and reported being more confident in their knowledge of the location of landmarks within the environment, compared with CRH. Results are discussed in terms of potential handedness differences in spatial ability generally.

Frontal cortex dysfunction as a target for remediation in opiate use disorder: Role in cognitive dysfunction and disordered reward systems.

In this chapter, we develop a model of µ- and δ-opioid receptor (OR) effects on cellular activity in the corticostriatal circuit after reviewing clinical data on cognitive and mood impairments in opioid substance use disorder (OUD), we use this model to derive information on the relevance of opioid actions in this circuit for cognition and reward. We find that the cognitive impairments and rewarding properties of acute µ-OR activation can reasonably explained by pharmacological actions in the corticostriatal circuit. However, long-term cognitive impairments and mood dysfunction observed in OUD are probably induced by opiate abuse-related degenerative mechanisms.