Non-spatially lateralized mechanisms in hemispatial neglect

Kim

et al. 2016

Human Brain Mapping

Self Cite

Few studies have directly compared the neural correlates of spatial attention (i.e., attention to a particular location) and nonspatial attention (i.e., attention to a feature in the visual scene) using well‐controlled tasks. Here, we investigated the neural correlates of spatial and nonspatial attention in humans using intracranial electroencephalography. The topography and number of electrodes showing significant event‐related desynchronization (ERD) or event‐related synchronization (ERS) in different frequency bands were studied in 13 epileptic patients. Performance was not significantly different between the two conditions. In both conditions, ERD in the low‐frequency bands and ERS in the high‐frequency bands were present bilaterally in the parietal cortex (prominently on the right hemisphere) and frontal regions. In addition to these common changes, spatial attention involved right‐lateralized activity that was maximal in the right superior parietal lobule (SPL), whereas nonspatial attention involved wider brain networks including the bilateral parietal, frontal, and temporal regions, but still had maximal activity in the right parietal lobe. Within the parietal lobe, spatial attention involved ERD or ERS in the right SPL, whereas nonspatial attention involved ERD or ERS in the right inferior parietal lobule. These findings reveal that common as well as different brain networks are engaged in spatial and nonspatial attention. Hum Brain Mapp 37:3041–3054, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Neural correlates of spatial and nonspatial attention determined using intracranial electroencephalographic signals in humans

Kim

et al. 2016

Human Brain Mapping

Self Cite

“…Current accounts of spatial neglect consider two fundamental attentional impairments: a non-spatial deficit of sustained attention (Robertson, 2001;Husain and Rorden, 2003) and a spatially lateralized bias favouring attentional orienting toward ipsilesional stimuli (Duncan et al, 1997;Driver and Mattingley, 1998;Pouget and Driver, 2000;Halligan et al, 2003). Evidence for this lateralized bias is the failure of neglect patients to be aware of a contralesional stimulus when an ipsilesional stimulus competes for attentional resources (Driver and Vuilleumier, 2001;Geeraerts et al, 2005) and their facilitated processing of right compared to left items (Smania et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

A non-spatial bias favouring fixated stimuli revealed in patients with spatial neglect

Ptak

Schnider

Golay

et al. 2007

Brain

The cardinal feature of spatial neglect is severely impaired exploration of the contralesional space, a failure resulting in unawareness of many contralesional stimuli. This deficit is exacerbated by a reflexive attentional bias toward ipsilesional items. Here we show that, in addition to these spatially lateralized failures, neglect patients also exhibit a severe bias favouring stimuli presented at fixation. We tested neglect patients and matched healthy and right-hemisphere damaged patients without neglect in a task requiring saccade execution to targets in the left or right hemifield. Targets were presented alone or simultaneously with a distracter that appeared in the same hemifield, in the opposite hemifield, or at fixation. We found two fundamental biases in saccade initiation of neglect patients: irrelevant distracters presented in the preserved hemifield tended to capture gaze reflexively, resulting in a large number of saccades erroneously directed toward the distracter. Additionally, distracters presented at fixation severely disrupted saccade initiation irrespective of saccade direction, leading to disproportionately increased latencies of left and right saccades. This latency increase was specific to oculomotor responses of neglect patients and was not observed when a manual response was required. These results show that, in addition to their failure to inhibit reflexive glances toward ipsilesional items neglect patients exhibit a strong oculomotor bias favouring fixated stimuli. We conclude that impaired initiation of saccades in any direction contributes to the deficits of spatial exploration that characterize spatial neglect.

“…Harrington et al [60] found deficits in duration perception (interval timing) in individuals with right hemisphere damage; moreover, the subjects' temporal performance was correlated with their ability to direct non-spatial attention. Based on patient studies, Husain & Rorden [61] suggested that the temporal-parietal junction (TPJ) encodes temporal information in the visual modality. Battelli et al [62,63] carried out a series of experiments on parietal neglect patients, and based on their findings, proposed that the right parietal lobe constitutes a 'when' cortical visual pathway.…”

Section: Neuropsychology Of Temporal Order Judgementsmentioning

confidence: 99%

Relative timing: from behaviour to neurons

Aghdaee

Battelli

Assad

2014

Phil. Trans. R. Soc. B

Processing of temporal information is critical to behaviour. Here, we review the phenomenology and mechanism of relative timing , ordinal comparisons between the timing of occurrence of events. Relative timing can be an implicit component of particular brain computations or can be an explicit, conscious judgement. Psychophysical measurements of explicit relative timing have revealed clues about the interaction of sensory signals in the brain as well as in the influence of internal states, such as attention, on those interactions. Evidence from human neurophysiological and functional imaging studies, neuropsychological examination in brain-lesioned patients, and temporary disruptive interventions such as transcranial magnetic stimulation (TMS), point to a role of the parietal cortex in relative timing. Relative timing has traditionally been modelled as a ‘race’ between competing neural signals. We propose an updated race process based on the integration of sensory evidence towards a decision threshold rather than simple signal propagation . The model suggests a general approach for identifying brain regions involved in relative timing, based on looking for trial-by-trial correlations between neural activity and temporal order judgements (TOJs). Finally, we show how the paradigm can be used to reveal signals related to TOJs in parietal cortex of monkeys trained in a TOJ task.