It has long been known that damage to the brain can produce a variety of different deficits of visual perception and attention (e.g., neglect, Balint's syndrome, visual agnosia). While the underlying causes of such deficits are often not well understood, recent attempts to apply advances from the study of normal cognitive functioning to the study of patients with brain injury have begun to increase our understanding of the precise nature of the mechanisms impaired by damage to different regions of the brain. During our last funding period, we used this strategy to isolate four distinct mechanisms involved in visual perception and attention which are selectively impaired by damage to different posterior cortical regions. The experiments in the present proposal will permit us to specify more precisely `the functional characteristics of each of these four mechanisms. Specifically, the proposed experiments will examine mechanisms involved in the analysis of hierarchically organized visual stimuli. Hierarchically organized stimuli are ones in which local level objects (e.g. eyes, nose, mouth) collectively form a global level object (e.g., a face). Our previous work has shown that a mechanism involved in local level analysis is affected by left temporal-parietal lesions while a mechanisms involved in global level analysis is affected by right temporal-parietal lesions. A third mechanism, involved in the integration of local and global information, is disrupted by lesions of either the left or the right-temporal-parietal area or by complete commissurotomy. Finally, the ability t~ shift attention between local and global objects is affected by rostral parietal lesions. The proposed experiments will determine what stimulus attributes are important for the functioning of each of these four mechanisms. Specifically, we will determine whether the functioning of a given mechanism is based on the hierarchical structure of the stimulus, on its spatial frequency content, or both. In addition, we will directly examine the relationship between perceptual analysis as it occurs with relatively simple """"""""artificial"""""""" stimuli typically used in the laboratory, and with the more complex """"""""naturalistic"""""""" stimuli encountered in the course of every day activities. This information is essential to the understanding of the perceptual and attentional deficits exhibited by patients with injury to different areas of posterior cortex and will also provide insight into how the normal intact visual stem functions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS027902-05A2
Application #
2266653
Study Section
Neurology A Study Section (NEUA)
Project Start
1990-01-01
Project End
1999-01-31
Budget Start
1995-02-01
Budget End
1996-01-31
Support Year
5
Fiscal Year
1995
Total Cost
Indirect Cost
Name
East Bay Institute for Research and Education
Department
Type
DUNS #
City
Martinez
State
CA
Country
United States
Zip Code
94553
Lamb, M R; Pond, H M; Zahir, G (2000) Contributions of automatic and controlled processes to the analysis of hierarchical structure. J Exp Psychol Hum Percept Perform 26:234-45
Lamb, M R; Yund, E W (2000) The role of spatial frequency in cued shifts of attention between global and local forms. Percept Psychophys 62:753-61
Lamb, M R; Yund, E W; Pond, H M (1999) Is attentional selection to different levels of hierarchical structure based on spatial frequency? J Exp Psychol Gen 128:88-94
Lamb, M R; Yund, E W (1996) Spatial frequency and attention: effects of level-, target-, and location-repetition on the processing of global and local forms. Percept Psychophys 58:363-73
Lamb, M R; Yund, E W (1993) The role of spatial frequency in the processing of hierarchically organized stimuli. Percept Psychophys 54:773-84
Robertson, L C; Lamb, M R (1991) Neuropsychological contributions to theories of part/whole organization. Cogn Psychol 23:299-330
Lamb, M R (1991) Attention in humans and animals: is there a capacity limitation at the time of encoding? J Exp Psychol Anim Behav Process 17:45-54
Robertson, L C; Lamb, M R; Knight, R T (1991) Normal global-local analysis in patients with dorsolateral frontal lobe lesions. Neuropsychologia 29:959-67
Lamb, M R; Robertson, L C (1990) The effect of visual angle on global and local reaction times depends on the set of visual angles presented. Percept Psychophys 47:489-96
Lamb, M R; Robertson, L C; Knight, R T (1990) Component mechanisms underlying the processing of hierarchically organized patterns: inferences from patients with unilateral cortical lesions. J Exp Psychol Learn Mem Cogn 16:471-83