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Wong C, Pearson KG, Lomber SG. Contributions of Parietal Cortex to the Working Memory of an Obstacle Acquired Visually or Tactilely in the Locomoting Cat. Cereb Cortex 2019; 28:3143-3158. [PMID: 28981640 DOI: 10.1093/cercor/bhx186] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Indexed: 01/15/2023] Open
Abstract
A working memory of obstacles is essential for navigating complex, cluttered terrain. In quadrupeds, it has been proposed that parietal cortical areas related to movement planning and working memory may be important for guiding the hindlegs over an obstacle previously cleared by the forelegs. To test this hypothesis, parietal areas 5 and 7 were reversibly deactivated in walking cats. The working memory of an obstacle was assessed in both a visually dependent and tactilely dependent paradigm. Reversible bilateral deactivation of area 5, but not area 7, altered hindleg stepping in a manner indicating that the animals did not recall the obstacle over which their forelegs had stepped. Similar deficits were observed when area 5 deactivation was restricted to the delay during which obstacle memory must be maintained. Furthermore, partial memory recovery observed when area 5 function was deactivated and restored within this maintenance period suggests that the deactivation may suppress, but not eliminate, the working memory of an obstacle. As area 5 deactivations incurred similar memory deficits in both visual and tactile obstacle working memory paradigms, parietal area 5 is critical for maintaining the working memory of an obstacle acquired via vision or touch that is used to modify stepping for avoidance.
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Affiliation(s)
- Carmen Wong
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada.,Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada
| | - Keir G Pearson
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - Stephen G Lomber
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada.,Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada.,Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.,Department of Psychology, University of Western Ontario, London, Ontario, Canada
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2
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Modified Origins of Cortical Projections to the Superior Colliculus in the Deaf: Dispersion of Auditory Efferents. J Neurosci 2018; 38:4048-4058. [PMID: 29610441 DOI: 10.1523/jneurosci.2858-17.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 03/13/2018] [Accepted: 03/16/2018] [Indexed: 11/21/2022] Open
Abstract
Following the loss of a sensory modality, such as deafness or blindness, crossmodal plasticity is commonly identified in regions of the cerebrum that normally process the deprived modality. It has been hypothesized that significant changes in the patterns of cortical afferent and efferent projections may underlie these functional crossmodal changes. However, studies of thalamocortical and corticocortical connections have refuted this hypothesis, instead revealing a profound resilience of cortical afferent projections following deafness and blindness. This report is the first study of cortical outputs following sensory deprivation, characterizing cortical projections to the superior colliculus in mature cats (N = 5, 3 female) with perinatal-onset deafness. The superior colliculus was exposed to a retrograde pathway tracer, and subsequently labeled cells throughout the cerebrum were identified and quantified. Overall, the percentage of cortical projections arising from auditory cortex was substantially increased, not decreased, in early-deaf cats compared with intact animals. Furthermore, the distribution of labeled cortical neurons was no longer localized to a particular cortical subregion of auditory cortex but dispersed across auditory cortical regions. Collectively, these results demonstrate that, although patterns of cortical afferents are stable following perinatal deafness, the patterns of cortical efferents to the superior colliculus are highly mutable.SIGNIFICANCE STATEMENT When a sense is lost, the remaining senses are functionally enhanced through compensatory crossmodal plasticity. In deafness, brain regions that normally process sound contribute to enhanced visual and somatosensory perception. We demonstrate that hearing loss alters connectivity between sensory cortex and the superior colliculus, a midbrain region that integrates sensory representations to guide orientation behavior. Contrasting expectation, the proportion of projections from auditory cortex increased in deaf animals compared with normal hearing, with a broad distribution across auditory fields. This is the first description of changes in cortical efferents following sensory loss and provides support for models predicting an inability to form a coherent, multisensory percept of the environment following periods of abnormal development.
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3
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Butler BE, de la Rua A, Ward-Able T, Lomber SG. Cortical and thalamic connectivity to the second auditory cortex of the cat is resilient to the onset of deafness. Brain Struct Funct 2017; 223:819-835. [PMID: 28940055 DOI: 10.1007/s00429-017-1523-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 09/04/2017] [Indexed: 10/18/2022]
Abstract
It has been well established that following sensory loss, cortical areas that would normally be involved in perceiving stimuli in the absent modality are recruited to subserve the remaining senses. Despite this compensatory functional reorganization, there is little evidence to date for any substantial change in the patterns of anatomical connectivity between sensory cortices. However, while many auditory areas are contracted in the deaf, the second auditory cortex (A2) of the cat undergoes a volumetric expansion following hearing loss, suggesting this cortical area may demonstrate a region-specific pattern of structural reorganization. To address this hypothesis, and to complement existing literature on connectivity within auditory cortex, we injected a retrograde neuronal tracer across the breadth and cortical thickness of A2 to provide the first comprehensive quantification of projections from cortical and thalamic auditory and non-auditory regions to the second auditory cortex, and to determine how these patterns are affected by the onset of deafness. Neural projections arising from auditory, visual, somatomotor, and limbic cortices, as well as thalamic nuclei, were compared across normal hearing, early-deaf, and late-deaf animals. The results demonstrate that, despite previously identified changes in A2 volume, the pattern of projections into this cortical region are unaffected by the onset of hearing loss. These results fail to support the idea that crossmodal plasticity reflects changes in the pattern of projections between cortical regions and provides evidence that the pattern of connectivity that supports normal hearing is retained in the deaf brain.
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Affiliation(s)
- Blake E Butler
- Cerebral Systems Laboratory, University of Western Ontario, London, ON, N6A 5C2, Canada. .,Department of Psychology, University of Western Ontario, London, ON, N6A 5C2, Canada. .,Brain and Mind Institute, University of Western Ontario, London, ON, N6A 5B7, Canada. .,National Centre for Audiology, University of Western Ontario, London, ON, N6G 1H1, Canada.
| | - Alexandra de la Rua
- Cerebral Systems Laboratory, University of Western Ontario, London, ON, N6A 5C2, Canada.,Neuroscience Undergraduate Program, University of Western Ontario, London, ON, N6A 3K7, Canada
| | - Taylor Ward-Able
- Cerebral Systems Laboratory, University of Western Ontario, London, ON, N6A 5C2, Canada.,Neuroscience Undergraduate Program, University of Western Ontario, London, ON, N6A 3K7, Canada
| | - Stephen G Lomber
- Cerebral Systems Laboratory, University of Western Ontario, London, ON, N6A 5C2, Canada.,Department of Psychology, University of Western Ontario, London, ON, N6A 5C2, Canada.,Brain and Mind Institute, University of Western Ontario, London, ON, N6A 5B7, Canada.,National Centre for Audiology, University of Western Ontario, London, ON, N6G 1H1, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, N6A 5C1, Canada
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4
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Origin of the thalamic projection to dorsal auditory cortex in hearing and deafness. Hear Res 2017; 343:108-117. [DOI: 10.1016/j.heares.2016.05.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/18/2016] [Accepted: 05/26/2016] [Indexed: 10/21/2022]
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5
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Butler BE, Chabot N, Kral A, Lomber SG. Origins of thalamic and cortical projections to the posterior auditory field in congenitally deaf cats. Hear Res 2016; 343:118-127. [PMID: 27306930 DOI: 10.1016/j.heares.2016.06.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 05/27/2016] [Accepted: 06/06/2016] [Indexed: 02/05/2023]
Abstract
Crossmodal plasticity takes place following sensory loss, such that areas that normally process the missing modality are reorganized to provide compensatory function in the remaining sensory systems. For example, congenitally deaf cats outperform normal hearing animals on localization of visual stimuli presented in the periphery, and this advantage has been shown to be mediated by the posterior auditory field (PAF). In order to determine the nature of the anatomical differences that underlie this phenomenon, we injected a retrograde tracer into PAF of congenitally deaf animals and quantified the thalamic and cortical projections to this field. The pattern of projections from areas throughout the brain was determined to be qualitatively similar to that previously demonstrated in normal hearing animals, but with twice as many projections arising from non-auditory cortical areas. In addition, small ectopic projections were observed from a number of fields in visual cortex, including areas 19, 20a, 20b, and 21b, and area 7 of parietal cortex. These areas did not show projections to PAF in cats deafened ototoxically near the onset of hearing, and provide a possible mechanism for crossmodal reorganization of PAF. These, along with the possible contributions of other mechanisms, are considered.
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Affiliation(s)
- Blake E Butler
- Department of Physiology and Pharmacology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada.
| | - Nicole Chabot
- Department of Physiology and Pharmacology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada
| | - Andrej Kral
- Department of Experimental Otology, Medical University Hannover, Germany; AudioNeuroTechnology, Medical University Hannover, Germany
| | - Stephen G Lomber
- Department of Physiology and Pharmacology, University of Western Ontario, Canada; Department of Psychology, University of Western Ontario, Canada; Brain and Mind Institute, University of Western Ontario, Canada; National Centre for Audiology, University of Western Ontario, Canada
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6
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Butler BE, Chabot N, Lomber SG. Quantifying and comparing the pattern of thalamic and cortical projections to the posterior auditory field in hearing and deaf cats. J Comp Neurol 2016; 524:3042-63. [DOI: 10.1002/cne.24005] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/21/2016] [Accepted: 03/24/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Blake E. Butler
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
| | - Nicole Chabot
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
| | - Stephen G. Lomber
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Department of Psychology; University of Western Ontario; London Ontario Canada N6A 5C2
- Brain and Mind Institute; University of Western Ontario; London Ontario Canada N6A 5B7
- National Centre for Audiology; University of Western Ontario; London Ontario Canada N6G 1H1
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7
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Butler BE, Chabot N, Lomber SG. A quantitative comparison of the hemispheric, areal, and laminar origins of sensory and motor cortical projections to the superior colliculus of the cat. J Comp Neurol 2016; 524:2623-42. [PMID: 26850989 DOI: 10.1002/cne.23980] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 02/03/2016] [Accepted: 02/03/2016] [Indexed: 11/11/2022]
Abstract
The superior colliculus (SC) is a midbrain structure central to orienting behaviors. The organization of descending projections from sensory cortices to the SC has garnered much attention; however, rarely have projections from multiple modalities been quantified and contrasted, allowing for meaningful conclusions within a single species. Here, we examine corticotectal projections from visual, auditory, somatosensory, motor, and limbic cortices via retrograde pathway tracers injected throughout the superficial and deep layers of the cat SC. As anticipated, the majority of cortical inputs to the SC originate in the visual cortex. In fact, each field implicated in visual orienting behavior makes a substantial projection. Conversely, only one area of the auditory orienting system, the auditory field of the anterior ectosylvian sulcus (fAES), and no area involved in somatosensory orienting, shows significant corticotectal inputs. Although small relative to visual inputs, the projection from the fAES is of particular interest, as it represents the only bilateral cortical input to the SC. This detailed, quantitative study allows for comparison across modalities in an animal that serves as a useful model for both auditory and visual perception. Moreover, the differences in patterns of corticotectal projections between modalities inform the ways in which orienting systems are modulated by cortical feedback. J. Comp. Neurol. 524:2623-2642, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Blake E Butler
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1.,Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7
| | - Nicole Chabot
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1.,Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7
| | - Stephen G Lomber
- Cerebral Systems Laboratory, University of Western Ontario, London, Ontario, Canada, N6A 5C2.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1.,Department of Psychology, University of Western Ontario, London, Ontario, Canada, N6A 5C2.,Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7.,National Centre for Audiology, University of Western Ontario, London, Ontario, Canada, N6G 1H1
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8
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Chabot N, Butler BE, Lomber SG. Differential modification of cortical and thalamic projections to cat primary auditory cortex following early- and late-onset deafness. J Comp Neurol 2015; 523:2297-320. [DOI: 10.1002/cne.23790] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 04/07/2015] [Accepted: 04/08/2015] [Indexed: 12/26/2022]
Affiliation(s)
- Nicole Chabot
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute, University of Western Ontario; London Ontario Canada N6A 5B7
| | - Blake E. Butler
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute, University of Western Ontario; London Ontario Canada N6A 5B7
| | - Stephen G. Lomber
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Psychology; University of Western Ontario; London Ontario Canada N6A 5C2
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario Canada N6A 5C1
- Brain and Mind Institute, University of Western Ontario; London Ontario Canada N6A 5B7
- National Centre for Audiology; University of Western Ontario; London Ontario Canada N6A 1H1
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9
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Wong C, Chabot N, Kok MA, Lomber SG. Amplified somatosensory and visual cortical projections to a core auditory area, the anterior auditory field, following early- and late-onset deafness. J Comp Neurol 2015; 523:1925-47. [DOI: 10.1002/cne.23771] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 02/25/2015] [Accepted: 02/26/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Carmen Wong
- Cerebral Systems Laboratory, University of Western Ontario; London Ontario N6A 5K8 Canada
- Graduate Program in Neuroscience; University of Western Ontario; London Ontario N6A 5K8 Canada
| | - Nicole Chabot
- Cerebral Systems Laboratory, University of Western Ontario; London Ontario N6A 5K8 Canada
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario N6A 5K8 Canada
| | - Melanie A. Kok
- Cerebral Systems Laboratory, University of Western Ontario; London Ontario N6A 5K8 Canada
- Graduate Program in Neuroscience; University of Western Ontario; London Ontario N6A 5K8 Canada
| | - Stephen G. Lomber
- Cerebral Systems Laboratory, University of Western Ontario; London Ontario N6A 5K8 Canada
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario N6A 5K8 Canada
- Department of Psychology; University of Western Ontario; London Ontario N6A 5K8 Canada
- Brain and Mind Institute, University of Western Ontario; London Ontario N6A 5K8 Canada
- National Centre for Audiology, University of Western Ontario; London Ontario N6A 5K8 Canada
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10
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Kok MA, Chabot N, Lomber SG. Cross-modal reorganization of cortical afferents to dorsal auditory cortex following early- and late-onset deafness. J Comp Neurol 2013; 522:654-75. [DOI: 10.1002/cne.23439] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 07/04/2013] [Accepted: 07/18/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Melanie A. Kok
- Graduate Program in Neuroscience; University of Western Ontario; London Ontario N6A 5C1 Canada
- Schulich School of Medicine and Dentistry; University of Western Ontario; London Ontario N6A 5C1 Canada
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario N6A 5C1 Canada
| | - Nicole Chabot
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario N6A 5C1 Canada
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario N6A 5C1 Canada
| | - Stephen G. Lomber
- Schulich School of Medicine and Dentistry; University of Western Ontario; London Ontario N6A 5C1 Canada
- Cerebral Systems Laboratory; University of Western Ontario; London Ontario N6A 5C1 Canada
- Department of Physiology and Pharmacology; University of Western Ontario; London Ontario N6A 5C1 Canada
- Department of Psychology; University of Western Ontario; London Ontario N6A 5C1 Canada
- Brain and Mind Institute, University of Western Ontario; London Ontario N6A 5C1 Canada
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11
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Carrasco A, Lomber SG. Influence of inter-field communication on neuronal response synchrony across auditory cortex. Hear Res 2013; 304:57-69. [DOI: 10.1016/j.heares.2013.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 05/21/2013] [Accepted: 05/27/2013] [Indexed: 11/25/2022]
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12
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Chabot N, Mellott JG, Hall AJ, Tichenoff EL, Lomber SG. Cerebral origins of the auditory projection to the superior colliculus of the cat. Hear Res 2013; 300:33-45. [PMID: 23500650 DOI: 10.1016/j.heares.2013.02.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 02/08/2013] [Accepted: 02/21/2013] [Indexed: 01/24/2023]
Abstract
The superior colliculus (SC) is critical for directing accurate head and eye movements to visual and acoustic targets. In visual cortex, areas involved in orienting of the head and eyes to a visual stimulus have direct projections to the SC. In auditory cortex of the cat, four areas have been identified to be critical for the accurate orienting of the head and body to an acoustic stimulus. These areas include primary auditory cortex (A1), the posterior auditory field (PAF), the dorsal zone of auditory cortex (DZ), and the auditory field of the anterior ectosylvian sulcus (fAES). Therefore, we hypothesized that these four regions of auditory cortex would have direct projections to the SC. To test this hypothesis, deposits of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) were made into the superficial and deep layers of the SC to label, by means of retrograde transport, the auditory cortical origins of the corticotectal pathway. Bilateral examination of auditory cortex revealed that the vast majority of the labeled cells were located in the hemisphere ipsilateral to the SC injection. In ipsilateral auditory cortex, nearly all the labeled neurons were found in the infragranular layers, predominately in layer V. The largest population of labeled cells was located in the fAES. Few labeled neurons were identified in A1, PAF, or DZ. Thus, in contrast to the visual system, only one of the auditory cortical areas involved in orienting to an acoustic stimulus has a strong direct projection to the SC. Sound localization signals processed in primary (A1) and other non-primary (PAF and DZ) auditory cortices may be transmitted to the SC via a multi-synaptic corticotectal network.
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Affiliation(s)
- Nicole Chabot
- Cerebral Systems Laboratory, Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario N6A 5K8, Canada
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13
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Reciprocal modulatory influences between tonotopic and nontonotopic cortical fields in the cat. J Neurosci 2010; 30:1476-87. [PMID: 20107075 DOI: 10.1523/jneurosci.5708-09.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Functional and anatomical studies suggest that acoustic signals are processed hierarchically in auditory cortex. Although most regions of acoustically responsive cortex are not tonotopically organized, all previous electrophysiological investigations of interfield interactions have only examined tonotopically represented areas. The purpose of the present study was to investigate the functional interactions between tonotopically and nontonotopically organized fields in auditory cortex. We accomplished this goal by examining the bidirectional contributions between the cochleotopically organized primary auditory cortex (A1) and the noncochleotopically organized second auditory field (A2). Multiunit acute recording procedures in combination with reversible cooling deactivation techniques were used in eight mature cats. The synaptic activity of A1 or A2 was suppressed while the neuronal response to tonal stimuli of the noninactivated area (A1 or A2) was measured. Response strength, neuronal threshold, receptive field bandwidths, and latency measures were collected at each recorded site before, during, and after cooling deactivation epochs. Our analysis revealed comparable changes in A1 and A2 neuronal response properties. Specifically, significant decreases in neuronal response strength, increases in neuronal threshold, and shortening of response latency were found in both fields during periods of cooling deactivation. The weak anatomical connections between the two fields investigated make these findings unexpected. Furthermore, the observed neuronal changes suggest a model of corticocortical interaction among auditory fields in which neither differences in the magnitude of anatomical projections nor cortical representation of sensory stimuli are reliable determinants of modulatory functions.
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14
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Mellott JG, Van der Gucht E, Lee CC, Carrasco A, Winer JA, Lomber SG. Areas of cat auditory cortex as defined by neurofilament proteins expressing SMI-32. Hear Res 2010; 267:119-36. [PMID: 20430082 DOI: 10.1016/j.heares.2010.04.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Revised: 02/22/2010] [Accepted: 04/05/2010] [Indexed: 10/19/2022]
Abstract
The monoclonal antibody SMI-32 was used to characterize and distinguish individual areas of cat auditory cortex. SMI-32 labels non-phosphorylated epitopes on the high- and medium-molecular weight subunits of neurofilament proteins in cortical pyramidal cells and dendritic trees with the most robust immunoreactivity in layers III and V. Auditory areas with unique patterns of immunoreactivity included: primary auditory cortex (AI), second auditory cortex (AII), dorsal zone (DZ), posterior auditory field (PAF), ventral posterior auditory field (VPAF), ventral auditory field (VAF), temporal cortex (T), insular cortex (IN), anterior auditory field (AAF), and the auditory field of the anterior ectosylvian sulcus (fAES). Unique patterns of labeling intensity, soma shape, soma size, layers of immunoreactivity, laminar distribution of dendritic arbors, and labeled cell density were identified. Features that were consistent in all areas included: layers I and IV neurons are immunonegative; nearly all immunoreactive cells are pyramidal; and immunoreactive neurons are always present in layer V. To quantify the results, the numbers of labeled cells and dendrites, as well as cell diameter, were collected and used as tools for identifying and differentiating areas. Quantification of the labeling patterns also established profiles for ten auditory areas/layers and their degree of immunoreactivity. Areal borders delineated by SMI-32 were highly correlated with tonotopically-defined areal boundaries. Overall, SMI-32 immunoreactivity can delineate ten areas of cat auditory cortex and demarcate topographic borders. The ability to distinguish auditory areas with SMI-32 is valuable for the identification of auditory cerebral areas in electrophysiological, anatomical, and/or behavioral investigations.
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Affiliation(s)
- Jeffrey G Mellott
- Centre for Brain and Mind, Department of Physiology & Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, Medical Sciences Building, Room 216, 1151 Richmond Street North, London, Ontario N6A 5C1, Canada
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15
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Auditory cortex projections target the peripheral field representation of primary visual cortex. Exp Brain Res 2008; 190:413-30. [PMID: 18641978 DOI: 10.1007/s00221-008-1485-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 06/24/2008] [Indexed: 10/21/2022]
Abstract
The purpose of the present study was to identify projections from auditory to visual cortex and their organization. Retrograde tracers were used to identify the sources of auditory cortical projections to primary visual cortex (areas 17 and 18) in adult cats. Two groups of animals were studied. In the first group, large deposits were centered on the lower visual field representation of the vertical meridian located along the area 17 and 18 border. Following tissue processing, characteristic patterns of cell body labeling were identified in extrastriate visual cortex and the visual thalamus (LGN, MIN, & LPl). In auditory cortex, of the four tonotopically-organized regions, neuronal labeling was identified in the supragranular layers of the posterior auditory field (PAF). Little to no labeling was evident in the primary auditory cortex, the anterior auditory field, the ventral posterior auditory field or in the remaining six non-tonotopically organized regions of auditory cortex. In the second group, small deposits were made into the central or peripheral visual field representations of primary visual cortex. Labeled cells were identified in PAF following deposits into regions of primary visual cortex representing peripheral, but not central, visual field representations. Furthermore, a coarse topography was identified in PAF, with neurons projecting to the upper field representation being located in the gyral portion of PAF and neurons projecting to the lower field representation located in the sulcal portion of PAF. Therefore, direct projections can be identified from tonotopically organized auditory cortex to the earliest stages of visual cortical processing.
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Lomber SG, Malhotra S, Sprague JM. Restoration of Acoustic Orienting Into a Cortically Deaf Hemifield by Reversible Deactivation of the Contralesional Superior Colliculus: The Acoustic “Sprague Effect”. J Neurophysiol 2007; 97:979-93. [PMID: 17151228 DOI: 10.1152/jn.00767.2006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Removal of all contiguous visual cortical areas of one hemisphere results in a contralateral hemianopia. Subsequent deactivation of the contralesional superior colliculus (SC) nullifies the effects of the visual cortex ablation and restores visual orienting responses into the cortically blind hemifield. This deficit nullification has become known as the “Sprague Effect.” Similarly, in the auditory system, unilateral ablation of auditory cortex results in severe sound localization deficits, as assessed by acoustic orienting, to stimuli in the contralateral hemifield. The purpose of this study was to examine whether auditory orienting responses can be restored into the impaired hemifield during deactivation of the contralesional SC. Three mature cats were trained to orient toward and approach an acoustic stimulus (broadband, white noise burst) that was presented centrally, or at one of 12 peripheral loci, spaced at 15° intervals. After training, a cryoloop was chronically implanted over the dorsal surface of the right SC. During cooling of the cooling loop to temperatures sufficient to deactivate the superficial and intermediate layers (SZ, SGS, SO, SGI), auditory orienting responses were eliminated into the left (contracooled) hemifield while leaving acoustic orienting into the right (ipsicooled) hemifield unimpaired. This deficit was temperature-dependently graded from periphery to center. After the effectiveness of the SC cooling loop was verified, auditory cortex of the middle and posterior ectosylvian and anterior and posterior sylvian gyri was removed from the left hemisphere. As expected, the auditory cortex ablation resulted in a profound deficit in orienting to acoustic stimuli presented at any position in the right (contralesional) hemifield, while leaving acoustic orienting into the left (ipsilesional) hemifield unimpaired. The ablations of auditory cortex did not have any impact on a visual detection and orienting task. The additional deactivation of the contralesional SC to temperatures sufficient to cool the superficial and intermediate layers nullified the deficit caused by the auditory cortex ablation and acoustic orienting responses were restored into the right hemifield. This restoration was temperature-dependently graded from center to periphery. The deactivations were localized and confirmed with reduced uptake of radiolabeled 2-deoxyglucose. Therefore deactivation of the right superior colliculus after the ablation of the left auditory cortex yields a fundamentally different result from that identified during deactivation of the right superior colliculus before the removal of left auditory cortex in the same animal. Thus the “Sprague Effect” is not unique to a particular sensory system and deactivation of the contralesional SC can restore either visual or acoustic orienting responses into an impaired hemifield after cortical damage.
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Affiliation(s)
- Stephen G Lomber
- Centre for Brain and Mind, Robarts Research Institute, University of Western Ontario, 100 Perth Drive, London, Ontario N6A 5K8, Canada.
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Malhotra S, Lomber SG. Sound localization during homotopic and heterotopic bilateral cooling deactivation of primary and nonprimary auditory cortical areas in the cat. J Neurophysiol 2006; 97:26-43. [PMID: 17035367 DOI: 10.1152/jn.00720.2006] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the contributions of primary auditory cortex (AI) to sound localization have been extensively studied in a large number of mammals, little is known of the contributions of nonprimary auditory cortex to sound localization. Therefore the purpose of this study was to examine the contributions of both primary and all the recognized regions of acoustically responsive nonprimary auditory cortex to sound localization during both bilateral and unilateral reversible deactivation. The cats learned to make an orienting response (head movement and approach) to a 100-ms broad-band noise stimulus emitted from a central speaker or one of 12 peripheral sites (located in front of the animal, from left 90 degrees to right 90 degrees , at 15 degrees intervals) along the horizontal plane after attending to a central visual stimulus. Twenty-one cats had one or two bilateral pairs of cryoloops chronically implanted over one of ten regions of auditory cortex. We examined AI [which included the dorsal zone (DZ)], the three other tonotopic fields [anterior auditory field (AAF), posterior auditory field (PAF), ventral posterior auditory field (VPAF)], as well as six nontonotopic regions that included second auditory cortex (AII), the anterior ectosylvian sulcus (AES), the insular (IN) region, the temporal (T) region [which included the ventral auditory field (VAF)], the dorsal posterior ectosylvian (dPE) gyrus [which included the intermediate posterior ectosylvian (iPE) gyrus], and the ventral posterior ectosylvian (vPE) gyrus. In accord with earlier studies, unilateral deactivation of AI/DZ caused sound localization deficits in the contralateral field. Bilateral deactivation of AI/DZ resulted in bilateral sound localization deficits throughout the 180 degrees field examined. Of the three other tonotopically organized fields, only deactivation of PAF resulted in sound localization deficits. These deficits were virtually identical to the unilateral and bilateral deactivation results obtained during AI/DZ deactivation. Of the six nontonotopic regions examined, only deactivation of AES resulted in sound localization deficits in the contralateral hemifield during unilateral deactivation. Although bilateral deactivation of AI/DZ, PAF, or AES resulted in profound sound localization deficits throughout the entire field, the cats were generally able to orient toward the hemifield that contained the acoustic stimulus, but not accurately identify the location of the stimulus. Neither unilateral nor bilateral deactivation of areas AAF, VPAF, AII, IN, T, dPE, nor vPE had any effect on the sound localization task. Finally, bilateral heterotopic deactivations of AI/DZ, PAF, or AES yielded deficits that were as profound as bilateral homotopic cooling of any of these sites. The fact that deactivation of any one region (AI/DZ, PAF, or AES) was sufficient to produce a deficit indicated that normal function of all three regions was necessary for normal sound localization. Neither unilateral nor bilateral deactivation of AI/DZ, PAF, or AES affected the accurate localization of a visual target. The results suggest that hemispheric deactivations contribute independently to sound localization deficits.
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Affiliation(s)
- Shveta Malhotra
- School of Behavioral and Brain Sciences, The University of Texas at Dallas, Richardson, TX, USA
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Rushmore RJ, Payne BR, Lomber SG. Functional impact of primary visual cortex deactivation on subcortical target structures in the thalamus and midbrain. J Comp Neurol 2005; 488:414-26. [PMID: 15973682 DOI: 10.1002/cne.20597] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The functional relationships between the primary visual cortex and its major subcortical target structures have long been a subject of interest. We studied these relationships by using localized cooling deactivation to silence portions of primary visual cortex and measuring 2-deoxyglucose (2DG) uptake to assess neural activity in subcortical and midbrain targets. We focused analysis on the largest subcortical targets of primary visual cortex: the superior colliculus (SC), the dorsal lateral geniculate nucleus of the thalamus (dLGN), and the lateral division of the lateral posterior nucleus of the thalamus (LPL). We found that localized cooling of different regions of primary visual cortex caused specific decreases in 2DG uptake in target structures such that the location of 2DG decrease varied according to joint retinotopy, and the magnitude of the decreases in target structures was associated with the amount of cooled cortex. In addition, we found that the impact of cortical cooling was more profound on the SC than on the dLGN. The functional impact of cortical deactivations on the LPL was weak for small deactivations but approximated the impact on the SC when deactivations were large. We discuss these findings in terms of neural circuits and in terms of drivers and modulators.
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Affiliation(s)
- R Jarrett Rushmore
- Cerebral Dynamics and Neural Plasticity, Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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Malhotra S, Hall AJ, Lomber SG. Cortical control of sound localization in the cat: unilateral cooling deactivation of 19 cerebral areas. J Neurophysiol 2004; 92:1625-43. [PMID: 15331649 DOI: 10.1152/jn.01205.2003] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the ability of mature cats to accurately orient to, and approach, an acoustic stimulus during unilateral reversible cooling deactivation of primary auditory cortex (AI) or 1 of 18 other cerebral loci. After attending to a central visual stimulus, the cats learned to orient to a 100-ms broad-band, white-noise stimulus emitted from a central speaker or 1 of 12 peripheral sites (at 15 degrees intervals) positioned along the horizontal plane. Twenty-eight cats had two to six cryoloops implanted over multiple cerebral loci. Within auditory cortex, unilateral deactivation of AI, the posterior auditory field (PAF) or the anterior ectosylvian sulcus (AES) resulted in orienting deficits throughout the contralateral field. However, unilateral deactivation of the anterior auditory field, the second auditory cortex, or the ventroposterior auditory field resulted in no deficits on the orienting task. In multisensory cortex, unilateral deactivation of neither ventral or dorsal posterior ectosylvian cortices nor anterior or posterior area 7 resulted in any deficits. No deficits were identified during unilateral cooling of the five visual regions flanking auditory or multisensory cortices: posterior or anterior ii suprasylvian sulcus, posterior suprasylvian sulcus or dorsal or ventral posterior suprasylvian gyrus. In motor cortex, we identified contralateral orienting deficits during unilateral cooling of lateral area 5 (5L) or medial area 6 (6m) but not medial area 5 or lateral area 6. In a control visual-orienting task, areas 5L and 6m also yielded deficits to visual stimuli presented in the contralateral field. Thus the sound-localization deficits identified during unilateral deactivation of area 5L or 6m were not unimodal and are most likely the result of motor rather than perceptual impairments. Overall, three regions in auditory cortex (AI, PAF, AES) are critical for accurate sound localization as assessed by orienting.
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Affiliation(s)
- Shveta Malhotra
- Cerebral Systems Laboratory, School of Behavioral and Brain Sciences, The University of Texas at Dallas, 2601 N. Floyd Road, GR41, Richardson, TX 75080, USA
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Payne BR, Cornwell P. Greater sparing of visually guided orienting behavior after early unilateral occipital lesions: insights from a comparison with the impact of bilateral lesions. Behav Brain Res 2004; 150:109-16. [PMID: 15033284 DOI: 10.1016/j.bbr.2003.07.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2003] [Revised: 07/01/2003] [Accepted: 07/01/2003] [Indexed: 10/27/2022]
Abstract
We know that cats with bilateral lesions of occipital visual cortical areas 17, 18 and 19 sustained during the first postnatal week exhibit a modest level of sparing of the ability to re-orient head and eyes to new stimuli relative to cats that incurred equivalent lesions in adulthood. We now report that cats with equivalent unilateral lesions sustained during the first postnatal week (P1-4), or at the end of the first postnatal month (P27-30), orient to stimuli presented in the contralesional field as proficiently as to stimuli introduced into the ipsilesional field. Moreover, levels of proficiency are indistinguishable from those exhibited by intact cats. Thus, the sparing is greater following unilateral lesions than following bilateral lesions, and the level of sparing approaches completeness. The difference between the bilateral and unilateral lesion results suggests types of pathway reorganizations that may emerge as a result of unilateral occipital lesions. We postulate that the greater sparing is based on modifications in both excitatory and inhibitory circuitry linked to the intact hemisphere, and we provide a framework for future investigations that should be relevant to the comprehension of the repercussions of early unilateral and bilateral lesions sustained by monkeys and humans, which also show more robust residual vision following early relative to later damage of occipital cortex.
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Affiliation(s)
- Bertram R Payne
- Department of Anatomy and Neurobiology, Center for Advanced Biomedical Research, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
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Payne BR. Limit of spared pattern vision following lesions of the immature visual cortex. Exp Brain Res 2003; 150:61-7. [PMID: 12698217 DOI: 10.1007/s00221-003-1387-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2002] [Accepted: 12/19/2002] [Indexed: 12/24/2022]
Abstract
Lesions of primary visual cortex sustained early in life spare certain aspects of visual processing that can be linked to expansions of bypass pathways to extrastriate cortex. They also trigger, in an age-dependent way, partial or complete transneuronal retrograde degeneration of beta (X) retinal ganglion cells, which are implicated in visual processing under conditions of low contrast. We used two-dimensional geometric patterns whose saliency was reduced by gradually increasing levels of superimposed masking lines, and by reductions in spatial contrast. Normative data were collected from intact cats, and baseline lesion data were collected from cats with lesions sustained as young adults (postnatal day 180, P180). Experimental data were collected from cats that sustained lesions on P1-3 or P26-30. For high contrast patterns, the adult group was impaired at both acquisition (sequential progressive levels of masking) and concurrent (parallel high and low levels of masking) performance, whereas the early-lesioned groups were impaired only at concurrent performance. All lesion groups were equally impaired when contrast was reduced to modest or lower levels. These results show that sparing of masked-pattern learning is limited to the high end of the spatial contrast domain.
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Affiliation(s)
- Bertram R Payne
- Department of Anatomy and Neurobiology, Center for Advanced Biomedical Research, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
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Payne BR, Lomber SG. Plasticity of the visual cortex after injury: what's different about the young brain? Neuroscientist 2002; 8:174-85. [PMID: 11954561 DOI: 10.1177/107385840200800212] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The repercussions of localized injury of the cerebral cortex in young brains differ from the repercussions triggered by equivalent damage of the mature brain. In the young brain, some distant neurons are more vulnerable to the lesion, whereas others survive and expand their projections to bypass damaged and degenerated structures. The net result is sparing of neural processing and behaviors. This article summarizes both the modifications in visual pathways resulting from visual cortex lesions sustained early in life and the neural and behavioral processes that are spared or permanently impaired. Experiments using reversible deactivation show that at least two highly localizable functions of normal cerebral cortex are remapped across the cortical surface as a result of an early lesion of the primary visual cortex. Moreover, the redistributions have spread the essential neural operations underlying orienting behavior from the visual parietal cortex to a normally functionally distinct type of cortex in the visual temporal system, and in the opposite direction for complex-pattern recognition. Similar functional reorganizations may underlie sparing of neural processes and behavior following early lesions in other cerebral systems, and these other systems may respond well to emerging therapeutic strategies designed to enhance the sparing of functions.
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Affiliation(s)
- Bertram R Payne
- Laboratory for Visual Perception and Cognition, Department of Anatomy and Neurobiology, Boston University School of Medicine, Massachusetts 02118, USA.
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Payne BR, Lomber SG, Gelston CD. Graded sparing of visually-guided orienting following primary visual cortex ablations within the first postnatal month. Behav Brain Res 2000; 117:1-11. [PMID: 11099752 DOI: 10.1016/s0166-4328(00)00276-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We compared the abilities of intact cats and cats that incurred lesions of areas 17 and 18 in adulthood, at one month of age (P28), or on the day of birth (P1), to detect and orient towards visual stimuli either moved into or illuminated in the periphery of the visual field, and to detect and orient towards a stationary, broad-band white-noise auditory stimulus. For all groups of cats, movement of a stimulus into the visual field was a more potent stimulus for evoking visually-guided orienting movements than illumination of a static light-emitting diode (LED). The potency of the auditory stimulus was also extremely high. Proficiency on both visual tasks was graded according to the age at which areas 17 and 18 were ablated in the sequence: adult, P1, P28 and intact in the sequence worst-->best performance. The superior performance of the P1- and P28-groups provided evidence for sparing of visually-guided orienting, but the sparing was incomplete because it did not match performance of intact cats. Lesions of areas 17 and 18 incurred in adulthood had no significant impact on orienting to auditory white-noise stimuli. However, orienting performance to auditory stimuli presented in the peripheral quadrants was slightly superior in the P28 group and reduced in the P1 group. Thus, the visual sparing exhibited by the P1 group may be at the expense of highly proficient orienting to auditory cues. Overall, these results extend our knowledge by showing that in addition to P1-cats, cats that incur lesions of areas 17 and 18 at one month-of-age also exhibit sparing of visually-guided orienting, and that the sparing is not confined to a single stimulation paradigm. Finally, the covariation in the magnitude of pathway modifications with the scale of the orienting proficiency in P1- and P28 cats helps to solidify the linkage between rewired brain pathways and spared visually-guided behaviors.
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Affiliation(s)
- B R Payne
- Department of Anatomy and Neurobiology, Center for Advanced Biomedical Research, Boston University School of Medicine, Boston, MA, 02118, USA.
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Payne BR, Lomber SG. A method to assess the functional impact of cerebral connections on target populations of neurons. J Neurosci Methods 1999; 86:195-208. [PMID: 10065986 DOI: 10.1016/s0165-0270(98)00166-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We describe an innovative and tested approach combining two individually potent techniques to visualize simultaneously the functional impact of multiple projections on target populations of neurons in the brain. The rationale is simple: silence a defined set of efferent projections from one cortical region using cooling deactivation and then measure the impact of the deactivation on activities in multiple target regions using 2-deoxyglucose (2DG). This is a straightforward and sound approach because 2DG uptake by neurons reflects levels of underlying neural activity. All distant modifications evoked by the silencing of the set of efferent projections are examined in anatomical tissue and simultaneously for the multiple target sites to provide a global view of the functional impacts of the set of projections on the targets. With this method, downward adjustments of 2DG uptake levels identify removals of net excitatory signals, whereas upward adjustments identify net removals of suppressive influences. Future possible uses and modifications of the technique, including optical imaging, are discussed. Overall, the technique has the potential to provide fundamental, new measures on cerebral network interactions that both complement and extend current static models of cerebral networks and electrophysiological measures of functional impacts on individual neurons.
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Affiliation(s)
- B R Payne
- Department of Anatomy and Neurobiology, Boston University School of Medicine, MA 02118, USA.
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Lomber SG, Payne BR. Removal of two halves restores the whole: reversal of visual hemineglect during bilateral cortical or collicular inactivation in the cat. Vis Neurosci 1996; 13:1143-56. [PMID: 8961543 DOI: 10.1017/s0952523800007781] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The purpose of the present study was to compare visual orienting behavior in the adult cat during (1) unilateral and bilateral cooling deactivation of posterior-middle suprasylvian (pMS) sulcal cortex, and (2) unilateral and bilateral deactivation of the superior colliculus. As expected, unilateral cooling deactivation of either pMS cortex or the superior colliculus resulted in a profound visual neglect of the contracooled hemifield. The addition of cooling the homotopic region in the opposite hemisphere largely reversed this deficit and restored visual orienting into the previously neglected hemifield. These results show that (1) pMS cortex and the superior colliculus are essential for normal detection and orienting to visual targets, and (2) unilateral visual neglect results from an imbalance of activities in the two hemispheres induced at either cortical or subcortical levels. These conclusions have implications for understanding neural bases of visual hemineglect following unilateral lesions in humans.
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Affiliation(s)
- S G Lomber
- Department of Anatomy and Neurobiology, Boston University School of Medicine, MA 02118, USA
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Payne BR, Lomber SG, Macneil MA, Cornwell P. Evidence for greater sight in blindsight following damage of primary visual cortex early in life. Neuropsychologia 1996; 34:741-74. [PMID: 8817506 DOI: 10.1016/0028-3932(95)00161-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This review compares the behavioral, physiological and anatomical repercussions of lesions of primary visual cortex incurred by developing and mature humans, monkey and cats. Comparison of the data on the repercussions following lesions incurred earlier or later in life suggests that earlier, but not later, damage unmasks a latent flexibility of the brain to compensate partially for functions normally attributed to the damaged cortex. The compensations are best documented in the cat and they can be linked to system-wide repercussions that include selected pathway expansions and neuron degenerations, and functional adjustments in neuronal activity. Even though evidence from humans and monkeys is extremely limited, it is argued on the basis of known repercussions and similarity of visual system organization and developmental sequence, that broadly equivalent repercussions most likely occur in humans and monkeys following early lesions of primary visual cortex. The extant data suggest potentially useful directions for future investigations on functional anatomical aspects of visual capacities spared in human patients and monkeys following early damage of primary visual cortex. Such research is likely to have a substantial impact on increasing our understanding of the repercussions that result from damage elsewhere in the developing cerebral cortex and it is likely to contribute to our understanding of the remarkable ability of the human brain to adapt to insults.
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Affiliation(s)
- B R Payne
- Laboratory of Visual Perception and Cognition, Boston University School of Medicine, MA 02118, USA
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