Behavioural Neurology - Volume 13, issue 1-2

Authors: Jackson, Stephen R.

Article Type: Research Article

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 1-2, 2002

Authors: McIntosh, R.D. | Pritchard, C.L. | Dijkerman, H.C. | Milner, A.D. | Roberts, R.C.

Article Type: Research Article

Abstract: Right hemisphere damaged patients with and without left visual neglect, and age-matched controls had objects of various sizes presented within left or right body hemispace. Subjects were asked to estimate the objects' sizes or to reach out and grasp them, in order to assess visual size processing in perceptual-experiential and action-based contexts respectively. No impairments of size processing were detected in the prehension performance of the neglect patients but a generalised slowing of movement was observed, …associated with an extended deceleration phase. Additionally both patient groups reached maximum grip aperture relatively later in the movement than did controls. For the estimation task it was predicted that the left visual neglect group would systematically underestimate the sizes of objects presented within left hemispace but no such abnormalities were observed. Possible reasons for this unexpected null finding are discussed. Show more

Keywords: visual neglect, hemimicropsia, perception, prehension, size distortion

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 3-15, 2002

Authors: Harvey, Monika | Jackson, Stephen R. | Newport, Roger | Krämer, Tanja | Morris, D. Llewlyn | Dow, Lindsay

Article Type: Research Article

Abstract: Patients with right unilateral cerebral stroke, four of which showed acute hemispatial neglect, and healthy aged-matched controls were tested for their ability to grasp objects located in either right or left space at near or far distances. Reaches were performed either in free vision or without visual feedback from the hand or target object. It was found that the patient group showed normal grasp kinematics with respect to maximum grip aperture, grip orientation, and the time …taken to reach the maximum grip aperture. Analysis of hand path curvature showed that control subjects produced straighter right hand reaches when vision was available compared to when it was not. The right hemisphere lesioned patients, however, showed similar levels of curvature in each of these conditions. No behavioural differences, though, could be found between right hemisphere lesioned patients with or without hemispatial neglect on either grasp parameters, path deviation or temporal kinematics. Show more

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 17-28, 2002

Authors: Gore, Christopher L. | Rodriguez, P. Dennis | Baylis, Gordon C.

Article Type: Research Article

Abstract: Patients with lesions to the right parietal lobe were tested on their ability to reach to targets, or to respond verbally to targets. The targets occurred at the same two spatial locations -- to the left and right of the patient -- with the task being cued by the color of the target. Patients were able to perform both tasks separately rapidly and without error. However, when the two tasks were interleaved, they had difficulty making a response in …the left (contralesional) field when this was different to a response that they had just made. These results suggest that lesions to the parietal cortex may cause a deficit in the coding for motor intention, as well as attention in the contralesional field. Show more

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 29-37, 2002

Authors: Behrmann, Marlene | Ghiselli-Crippa, Thea | Dimatteo, Ilaria

Article Type: Research Article

Abstract: Patients with unilateral neglect are impaired at making saccades to contralesional targets. Whether this problem arises from a deficit in perception, in planning the saccade or in executing the eye movement or some combination thereof remains unclear. We measured several variables related to the initiation and execution of saccades in an experiment which crossed two factors: target side (left, right) and direction of saccade (leftwards, rightwards). Relative to control subjects, patients with left-sided neglect …were impaired in planning but not executing the contralesional saccade; while the latency to move their eyes following the onset of the target was increased, the duration and velocity to reach the target were normal. In addition, there were also no directional differences for saccades that were hypometric or inaccurate in the patients, further ruling out an execution impairment. Interestingly, this directional initiation deficit was exaggerated for leftward saccades to left targets, compared with all other conditions. We suggest that the disadvantage for contralesional saccades in neglect patients is attributable to a deficit not only in perceiving contralateral targets but also in planning leftward saccades. Once the saccade is initiated, however, execution apparently proceeds unimpaired. Show more

Keywords: eye movements, saccades, hemispatial neglect, parietal cortex

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 39-60, 2002

Authors: di Pellegrino, Giuseppe | Làdavas, Elisabetta | Galletti, Claudio

Article Type: Research Article

Abstract: Neglect dyslexia is a disturbance in the allocation of spatial attention over a letter string following unilateral brain damage. Patients with this condition may fail to read letters on the contralesional side of an orthographic string. In some of these cases, reading is better with words than with non-words. This word superiority effect has received a variety of explanations that differ, among other things, with regard to the spatial distribution of attention across the letter string …during reading. The primary goal of the present study was to explore the interaction between attention and lexical processes by recording eye movements in a patient (F.C.) with severe left neglect dyslexia who was required to read isolated word and non-word stimuli of various length. F.C.'s ocular exploration of orthographic stimuli was highly sensitive to the lexical status of the letter string. We found that: (1) the location to which F.C. directed his initial saccade (obtained approximately 230 ms post-stimulus onset) differed between word and non-word stimuli; (2) the patient spent a greater amount of time fixating the contralesional side of word than non-word strings. Moreover, we also found that F.C. failed to identify the left letters of a string despite having fixated them, thus showing a clear dissociation between eye movement responses and conscious access to orthographic stimuli. Our data suggest the existence of multiple interactions between lexical, attentional and eye movement systems that occur from very initial stages of visual word recognition. Show more

Keywords: neglect dyslexia, eye movement, lexical access, spatial attention, reading

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 61-74, 2002

Authors: Humphreys, Glyn W. | Riddoch, M. Jane

Article Type: Research Article

Abstract: We examined search for target objects in a patient, MP, showing symptoms of left unilateral neglect. The conditions varied how the target was defined, the numbers of targets and distractors, and whether search was for multiple or single targets. We found that search was substantially improved when the target was defined by a description of its action rather than its name. This advantage for action-defined targets increased with larger display sizes. For both action and name-defined …targets, there were also larger effects of the number of distractors when search was for multiple rather than single targets, even when the numbers of distractors were kept constant. However, these effects were increased for name-defined targets. The differences between action- and name-defined targets decreased when objects were replaced with words. The data suggest that search could be based on action-defined templates of targets, activated by affordances from objects. The action-defined templates facilitated detection and reduced MP's tendency to re-search displays. Show more

Citation: Behavioural Neurology, vol. 13, no. 1-2, pp. 75-87, 2002