Effects of memory load on hemispheric asymmetries of colour memory

Abstract

Hemispheric asymmetries in colour perception have been a matter of debate for some time. Recent evidence suggests that lateralisation of colour processing may be largely task specific. Here we investigated hemispheric asymmetries during different types and phases of a delayed colour-matching (recognition) memory task. A total of 11 male and 12 female right-handed participants performed colour-memory tasks. The task involved presentation of a set of colour stimuli (encoding), and subsequent indication (forced choice) of which colours in a larger set had previously appeared at the retrieval or recognition phase. The effect of memory load (set size), and the effect of lateralisation at the encoding or retrieval phases were investigated. Overall, the results indicate a right hemisphere advantage in colour processing, which was particularly pronounced in high memory load conditions, and was seen in males rather than female participants. The results suggest that verbal (mnemonic) strategies can significantly affect the magnitude of hemispheric asymmetries in a non-verbal task.

Lateral Bias in Visual Working Memory

“…In an early psychophysical study [26], participants were asked to memorize either digits (verbal memory task) or digit positions (spatial memory task) presented for 80 ms in the right or left visual half-field. Similar to Clapp et al [15], the results revealed visual half-field and sex/gender-specific findings: men recalled more digits (verbal memory) from the RVF than LVF, whereas women did not show any performance differences between visual half-fields. In addition, the recall of digit positions (i.e., spatial memory) did not differ as a function of the visual hemi-field despite the classical of a RH specialization for the spatial component of WM (e.g., [27,28]).…”

“…This advantage was most pronounced in a high compared to low memory load condition and was interpreted by the authors as RH superiority in encoding and retrieval of color stimuli when memory load is high, and a stronger LH involvement (i.e., reduced asymmetry) when memory load is low, probably due to a LH verbalization strategy when memorizing color stimuli. Notably, in this study, the LVF/RH advantage was found in 90% of men but only in 60% of women [15]. In an early psychophysical study [26], participants were asked to memorize either digits (verbal memory task) or digit positions (spatial memory task) presented for 80 ms in the right or left visual half-field.…”

“…Some of these studies reported faster and more accurate responses towards serially presented words in the RVF as compared to LVF, suggesting a RVF/LH advantage following lateralized encoding [18] and retrieval [19]. The lateralized color WM study [15] revealed LVH/RH advantage in accuracy for both encoding and retrieval. This advantage was most pronounced in a high compared to low memory load condition and was interpreted by the authors as RH superiority in encoding and retrieval of color stimuli when memory load is high, and a stronger LH involvement (i.e., reduced asymmetry) when memory load is low, probably due to a LH verbalization strategy when memorizing color stimuli.…”

“…The bilateral version of the change-detection VWM task allows to differentiate between ipsi-and contralateral visual pathways as stimuli presented to the right and left visual half-fields are dominantly processed by the left and right hemispheres, respectively. However, in the majority of studies using the bilateral change-detection task, contra-and ipsilateral brain responses and performance have been investigated without taking into account the visual half-field to which attention has been directed (e.g., [2,[11][12][13][14]), and the studies that included visual half-field in the statistical design reported contradictory results [15][16][17][18][19][20][21][22][23][24][25]. Some of these studies reported faster and more accurate responses towards serially presented words in the RVF as compared to LVF, suggesting a RVF/LH advantage following lateralized encoding [18] and retrieval [19].…”