what are the four models of language?
- connectionist model (classification systems)
- computational model
neuropsychological model - contemporary neurobiological model
what is the key limitation of the dominant connectionist paradigm?
only about 30% of aphasic individuals fit neatly into these categories
Connectionist Classification System:
the term aphasia applies to…
language-specific behaviors (not the anatomy, physiology, or cognitive mechanism)
Connectionist Classification System:
- adopted by aphasia diagnostic standardized batteries
- most commonly used
- incorporates both behavioral characteristics and neuroanatomical correlates of the observed behaviors
Connectionist Classification System:
what is it termed “connectionist” model?
because of the inherent assumption that the various aphasic subtypes reflect disruption of specific brain centers or the connections between these centers
Connectionist Classification System:
assumes the existence of language centers located in what discrete regions of the brain?
Wernicke’s area (posterior center) and Broca’s area (anterior center)
Wernicke’s center (posterior center)
- holds auditory language representation
- a lesion in this center not only impairs auditory comprehension but also influences speech production
Broca’s area (anterior center)
- holds speech motor representations
- a lesion in this center disrupts spoken word production but leaves but leaves auditory comprehension intact (just a theory) - impacts the way they are talking, planning and programming issues
Disruption of the arcuate fasciculus connecting posterior and anterior language centers is assumed to cause…
auditory repetition deficits (e.g., conduction aphasia)
Computational Model
- holds that various aspects of language can be represented as patterns of activity over interconnected sets of simple neuronlike processing units that occur in a competitive cooperative fashion
Computational Model
patterns of activity within this architecture are enabled through differentially weighted connections between units
- a word is linked to specific processing unit/note
- have been used to model aphasic errors (e.g., paraphasias)
Cognitive Neuropsychological Model
(semantic system)
- language is no longer understood in terms of anatomical functions but instead has several identifiable processing components leading to the end point = word production
Cognitive Neuropsychological Model
(semantic system)
- the study of individuals with brain injury can inform our understanding of normal language processes
- brain damage can disrupts a model or processing component selectively, leaving other components to operate normally
- provide a framework for assessment and treatment
Contemporary Neurobiological Models of Language
the brain words more like a dynamic network with plasticity, gray and white matter are part of the same interactive process
Contemporary Neurobiological Models of Language:
Dual stream model = 2 major pathways:
Dorsal stream and ventral stream
dorsal stream:
supported mainly by the superior longitudinal fasciculus and arcuate fasciculus, associated with phonological processing
ventral stream:
supported mainly by the inferior fronto-occipital fasciculus, associated with semantic processing
FAT (Frontal Aslant Tract):
connecting the supplementary motor area to the Broca’s area, plays a role in driving and initiating speech
