Left Visual Field-right Hemisphere Advantage Research Articles

Exploring the relationship between response time, sensitivity and bias in categorical and coordinate visuospatial processes: Evidence for hemispheric specialisation

Right visual field-left hemisphere (RVF-LH) and left visual field-right hemisphere (LVF-RH) specialisations found for categorical and coordinate visuospatial judgements, respectively, are thought to demonstrate two different perceptual processes. In the current experiment, we used signal detection theory to investigate categorical and coordinate processes, and to explore the relationship between response time (RT), sensitivity and bias measures. We found a LVF-RH advantage for the processing of categorical spatial relations when this effect was indexed by sensitivity. We also found that task influenced response bias in RVF-LH trials, but not in LVF-RH trials. Increased sensitivity was correlated with faster responses in the coordinate task but slower responses in the categorical task, and faster RTs when responding liberally in RVF-LH but not LVF-RH categorical trials. By analysing signal detection measures alongside RT, the findings suggest that differences in sensitivity and response bias may contribute to typical task by hemisphere effects in RT.

Hemispheric asymmetries for temporal information processing: Transient detection versus sustained monitoring

This study investigated functional differences in the processing of visual temporal information between the left and right hemispheres (LH and RH). Participants indicated whether or not a checkerboard pattern contained a temporal gap lasting between 10 and 40 ms. When the stimulus contained a temporal signal (i.e. a gap), responses were more accurate for the right visual field-left hemisphere (RVF-LH) than for the left visual field-right hemisphere (LVF-RH). This RVF-LH advantage was larger for the shorter gap durations (Experiments 1 and 2), suggesting that the LH has finer temporal resolution than the RH, and is efficient for transient detection. In contrast, for noise trials (i.e. trial without temporal signals), there was a LVF-RH advantage. This LVF-RH advantage was observed when the entire stimulus duration was long (240 ms, Experiment 1), but was eliminated when the duration was short (120 ms, Experiment 2). In Experiment 3, where the gap was placed toward the end of the stimulus presentation, a LVF-RH advantage was found for noise trials whereas the RVF-LH advantage was eliminated for signal trials. It is likely that participants needed to monitor the stimulus for a longer period of time when the gap was absent (i.e. noise trials) or was placed toward the end of the presentation. The RH may therefore be more efficient in the sustained monitoring of visual temporal information whereas the LH is more efficient for transient detection.

Flexible contrast gain control in the right hemisphere

This study investigates whether the right hemisphere has more flexible contrast gain control settings for the identification of spatial frequency. Right-handed participants identified 1 and 9 cycles per degree sinusoidal gratings presented either to the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH). When luminance contrast was randomized across a wide range (20–60%), performance gradually improved with contrast in the LVF-RH. Conversely, performance in the RVF-LH was disrupted and saturated for 20 and 60% of contrast, respectively, leading to a LVF-RH advantage for these contrast levels. When contrast was blocked or randomized for a smaller range (30–50%), the LVF-RH advantage was diminished. Flexible contrast gain control is needed when contrast is randomized across a wide range, but not when it is blocked or randomized across a smaller range. The results therefore suggest that the right hemisphere is able to process spatial frequency information across a wider range of contrast levels than is the left hemisphere.

Hemispheric asymmetry in temporal resolution: Contribution of the magnocellular pathway

Right-handed participants performed simple visual judgments on nonverbal stimuli presented either to the left visual field-right hemisphere (LVF-RH) or to the right visual field-left hemisphere (RVF-LH). The stimuli were exposed for 40-120 msec, followed by a backward mask. When the stimuli were presented against a green background, an RVF-LH advantage was observed for the shortest exposure duration. This result supports the notion that the LH has finer temporal resolution than the RH. Imposition of a red background disrupted performance and eliminated the RVF-LH advantage for the shortest exposure duration. Because the red background attenuates functions of the magnocellular pathway, these results suggest that the magnocellular pathway contributes to the LH advantage for fine temporal resolution.

The Role of High Spatial Frequencies in Hemispheric Processing of Categorical and Coordinate Spatial Relations

Right-handed participants performed categorical and coordinate spatial relation tasks on stimuli presented either to the left visual field-right hemisphere (LVF-RH) or to the right visual field-left hemisphere (RVF-LH). The stimuli were either unfiltered or low-pass filtered (i.e., devoid of high spatial frequency content). Consistent with previous studies, the unfiltered condition produced a significant RVF-LH advantage for the categorical task and an LVF-RH advantage for the coordinate task. Low-pass filtering eliminated this Task x Visual Field interaction; thus, the RVF-LH advantage disappeared for the categorical task. The present results suggest that processing of high spatial frequency contributes to the left hemispheric advantage for categorical spatial processing.

Hemispheric processing of categorical and coordinate spatial relations in the absence of low spatial frequencies.

Right-handed participants performed the categorical and coordinate spatial relation judgments on stimuli presented to either the left visual field - right hemisphere (LVF-RH) or the right visual field - left hemisphere (RVF-LH). The stimulus patterns were formulated either by bright dots or contrast-balanced dots. When the stimuli were bright, an RVF-LH advantage was observed for the categorical task, whereas an LVF-RH advantage was observed for the coordinate task. When the stimuli were contrast balanced, the RVF-LH advantage was observed for the categorical task, but the LVF-RH advantage was eliminated for the coordinate task. Because the contrast-balanced dots are largely devoid by of low spatial frequency content, these results suggest that processing of low spatial frequency is responsible for the right hemisphere advantage for the coordinate spatial processing.

Comparative Assessment of Distance Processing and Hemispheric Specialization in Humans and Baboons (Papio papio)

This comparative study explored the ability to process distance and its lateralization in humans and baboons. Using a conditional matching-to-sample procedure in a divided-field format, subjects had to decide whether or not the distance between a line and a dot belonged to a short- or a long-distance category. Experiments 1, 2, and 4 demonstrated the ability of baboons to process and categorize distances. Moreover, humans showed better distance processing for right visual field/left hemisphere presentations than for left visual field/right hemisphere (LVF-RH) displays (Experiments 1–2). The same bias was found in baboons (Experiment 1), but in a weaker way. In Experiment 3, naive human individuals were tested and the difficulty of the discrimination was enhanced. There was a LVF-RH advantage which vanished with practice. Results are discussed by referring to theories (i.e., Kosslyn, 1987) of visuospatial processing for coordinate and categorical judgments.

Hemispheric specialization for categorical and coordinate spatial representations: a reappraisal.

The purpose of the present study was to examine Kosslyn's (1987) claim that the left hemisphere (LH) is specialized for the computation of categorical spatial representations and that the right hemisphere (RH) is specialized for the computation of coordinate spatial representations. Categorical representations involve making judgements about the relative position of the components of a visual stimulus (e.g., whether one component is above/below another). Coordinate representations involve calibrating absolute distances between the components of a visual stimulus (e.g., whether one component is within 5 mm of another). Thirty-two male and 32 female undergraduates were administered two versions of a categorical or a coordinate task over three blocks of 36 trials. Within each block, items were presented to the right visual field-left hemisphere (RVF-LH), the left visual field-right hemisphere (LVF-RH), or a centralized position. Overall, results were more supportive of Kosslyn's assertions concerning the role played by the RH in the computation of spatial representations. Specifically, subjects displayed an LVF-RH advantage when performing both versions of the coordinate task. The LVF-RH advantage on the coordinate task, however, was confirmed to the first block of trials. Finally, it was found that males were more likely than females to display faster reaction times (RTs) on coordinate tasks, slower RTs on categorical tasks, and an LVF-RH advantage in computing coordinate tasks.

Hemispheric asymmetry in the processing of absolute versus relative spatial frequency

Observers indicated whether a stimulus presented to one visual field or the other consisted of two sine-wave gratings (the baseline stimulus) or those same two gratings with the addition of a 2 cycle per degree (cpd) component. When the absolute spatial frequencies of the baseline stimulus were low (0.5 and 1.0 cpd), there was a left visual field-right hemisphere (LVF-RH) advantage in reaction time (RT) to respond to the baseline stimulus which disappeared when the 2 cpd component was added (i.e., the stimulus consisted of 0.5, 1.0, and 2.0 cpd components). When the absolute spatial frequencies of the baseline stimulus were moderate to high (4.0 and 8.0 cpd), a right visual field-left hemisphere advantage in RT to respond to the baseline stimulus approached significance and shifted to a significant LVF-RH advantage when the 2 cpd component was added (i.e., the stimulus consisted of 2.0, 4.0, and 8.0 cpd components. That is, adding the same 2 cpd component caused opposite shifts in visual laterality depending on whether 2 cpd was a relatively high or relatively low frequency compared to the baseline.

Hemispheric differences in the rates of information processing for simple non-verbal stimuli

An inspection time task, used to gauge differences in speed of information processing between the hemispheres, was administered to 22 normal subjects. It was found that the left visual field-right hemisphere (LVF-RH) exhibited an inferior performance relative to the right visual field-left hemisphere (RVF-LH). These results were consistent with other studies which have found an RVF-LH advantage for the processing of temporal/serial information. The possible ramifications of these results for models of asymmetry which do and do not attribute the left hemisphere's preferential capacity for language to these fundamental processes are then discussed.

Effects of a concurrent memory task on hemispheric asymmetries in categorization

Recent research on the division of processing between the two cerebral hemispheres has often employed two concurrent tasks to investigate the dynamic nature of hemispheric asymmetries. The experiment reported here explored the effects of two concurrent high-level cognitive tasks (memory retention and semantic categorization) on the direction and magnitude of hemispheric differences in the processing of words and pictures. Subjects were required to categorize words and pictures presented to either the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH). The categorization could be performed while holding either verbal material in memory (digit span), pictorial material in memory (serial nonsense figure recognition), or with no concurrent memory task. The effects produced hemisphere-specific, material-nonspecific interference. The verbal task removed a RVF-LH advantage at word categorization and enhanced a LVF-RH advantage on picture categorization; the pictorial task interfered with picture categorization in the LVF-RH, while enhancing a RVF-LH advantage at word categorization. The results are discussed in terms of multiple resource models of hemisphere function, capacity limitations, and the functional locus of processing required to produce various dynamic hemispheric effects.

SES-related Aspects of Neuropsychological Performance

Children from different socioeconomic backgrounds have been observed to employ different cognitive styles in problem-solving situations. These cognitive styles have in turn been linked to the functional specialization of the cerebral hemispheres. It was hypothesized, therefore, that performance asymmetries would also be SES-related, high-SES children processing stimuli presented to the right visual field-left hemisphere (RVF-LH) more efficiently than those presented to the left visual field-right hemisphere (LVF-RH) and low-SES children showing the reverse pattern. A laterality task was administered tachistoscopically to 120 children, divided evenly by SES (high and low), sex, and grade (fifth and seventh). A marked RVF-LH advantage emerged among the high-SES group and a weak LVF-RH advantage among the low-SES group. Thus, the results provided general support for the central hypothesis. The findings are reviewed in the context of current models of human information processing in the cerebral hemispheres, and their broader implications for understanding SES-related differences in cognitive function are discussed.

Right hemisphere superiority for initial stages of letter processing

When single letters, which could be perfectly recognized when presented alone, were embedded in an overlapping masking stimulus, observers recognized more letters from the left than from the right visual field. This left visual field-right hemisphere advantage persisted over short time intervals between the letter and the mask, regardless of which stimulus occurred first. Such results suggest that the right cerebral hemisphere is more efficient than the left at extracting relevant visual features of letters when the letters are perceptually degraded, even though letters are highly associated with language and, therefore, readily processed along verbal-analytic dimensions.