Neural System Imbalances and the Consequence of Large Brain Injuries

LeVere, T. E.

doi:10.1007/978-1-4613-0941-3_2

Cited by 12 publications

(7 citation statements)

References 32 publications

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“…New neural growth can occur following central nervous system damage, even in the aged brain, although it may be limited and it can have negative as well as positive effects (Kolb 1996; Le Vere 1988). Neural reorganizational mechanisms exist, allowing new connections between neurones at local and distant sites, including increased efficiency of neural transmission, dendritic branching, synaptic remodelling, and axonal sprouting (e.g., Blomert 1997;Kolb 1996).…”

Section: Re-assembling the Brain: Are Cell Assemblies The Brain's Lanmentioning

confidence: 99%

“…Smaller lesions may produce restoration through neural sparing, allowing some repair to assemblies. In large lesions, however, compensation appears to occur using intact assemblies not originally concerned with the lost functions and perhaps even distant from the original assemblies (Cotman & Nieto-Sampedro 1982; Kolb 1996; Le Vere 1988). Smaller lesions allowing compensation by intact assemblies might produce some short-term behavioral gains but may suppress the only partially damaged assemblies that subserved the impaired function.…”

Section: Re-assembling the Brain: Are Cell Assemblies The Brain's Lanmentioning

confidence: 99%

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Words in the brain's language

1999

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If the cortex is an associative memory, strongly connected cell assemblies will form when neurons in different cortical areas are frequently active at the same time. The cortical distributions of these assemblies must be a consequence of where in the cortex correlated neuronal activity occurred during learning. An assembly can be considered a functional unit exhibiting activity states such as full activation (“ignition”) after appropriate sensory stimulation (possibly related to perception) and continuous reverberation of excitation within the assembly (a putative memory process). This has implications for cortical topographies and activity dynamics of cell assemblies forming during language acquisition, in particular for those representing words. Cortical topographies of assemblies should be related to aspects of the meaning of the words they represent, and physiological signs of cell assembly ignition should be followed by possible indicators of reverberation. The following postulates are discussed in detail: (1) assemblies representing phonological word forms are strongly lateralized and distributed over perisylvian cortices; (2) assemblies representing highly abstract words such as grammatical function words are also strongly lateralized and restricted to these perisylvian regions; (3) assemblies representing concrete content words include additional neurons in both hemispheres; (4) assemblies representing words referring to visual stimuli include neurons in visual cortices; and (5) assemblies representing words referring to actions include neurons in motor cortices. Two main sources of evidence are used to evaluate these proposals: (a) imaging studies focusing on localizing word processing in the brain, based on stimulus-triggered event-related potentials (ERPs), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI), and (b) studies of the temporal dynamics of fast activity changes in the brain, as revealed by high-frequency responses recorded in the electroencephalogram (EEG) and magnetoencephalogram (MEG). These data provide evidence for processing differences between words and matched meaningless pseudowords, and between word classes, such as concrete content and abstract function words, and words evoking visual or motor associations. There is evidence for early word class-specific spreading of neuronal activity and for equally specific high-frequency responses occurring later. These results support a neurobiological model of language in the Hebbian tradition. Competing large-scale neuronal theories of language are discussed in light of the data summarized. Neurobiological perspectives on the problem of serial order of words in syntactic strings are considered in closing.

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Section: Re-assembling the Brain: Are Cell Assemblies The Brain's Lanmentioning

confidence: 99%

Section: Re-assembling the Brain: Are Cell Assemblies The Brain's Lanmentioning

confidence: 99%

Words in the brain's language

1999

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“…The amount of this recovery, however, is an entirely different matter, and it is often hotly debated. The issue underlying these debates is not really how much behavioral recovery can, and/or will, occur, but rather how to define behavioral recovery (see LeVere, 1988) .…”

Section: Discussionmentioning

confidence: 99%

Recovery of function after brain damage: The effects of nimodipine on the chronic behavioral deficit

LeVere

1993

Psychobiology

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“…LeVere (9). However, it has not been specifically shown that similar compensatory shifts may result from motor deficits consequent to brain injury.…”

Section: Introductionmentioning

confidence: 99%

Visual Cortex Hyperactivity During Arm Movements in Brain Injured Individuals: Evidence of Compensatory Shifts in Functional Neural Systems

Blood¹,

Perlman²,

Balliet³

et al. 1991

Neurorehabilitation and Neural Repair

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Basic neural mechanisms associated with recovery after brain injury were evaluated. Positron-emission tomography (PET) and fluorine-18-labeled fluorodeoxyglucose (18-FDG) were utilized to measure glucose metabolism and associated brain activity in the area of the visual cortex during motor tasks in post-acute brain injured (BI) young adults. Four hemiplegic BI subjects were compared over time to four normal matched controls for affected arm movement, least affected arm movement, and rest conditions. Initial data demonstrated hyperactivity in the visual cortex of the BI group versus the control group. Also, in subsequent data under higher resolution conditions greater visual cortex hyperactivity in the BI group was associated with more difficult movement tasks. These results support the hypothesis that compensatory shifts in functional neural systems occur in the visual cortex of post-acute brain injured adults.

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Neural System Imbalances and the Consequence of Large Brain Injuries

Cited by 12 publications

References 32 publications

Words in the brain's language

Words in the brain's language

Recovery of function after brain damage: The effects of nimodipine on the chronic behavioral deficit

Visual Cortex Hyperactivity During Arm Movements in Brain Injured Individuals: Evidence of Compensatory Shifts in Functional Neural Systems

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