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Short review:

T. Zawidzki, W. Bechtel, Galls Legacy Revisited: Decomposition and Localization in

Cognitive Neuroscience [in:] Erneling, Ch., Johnson, D. (eds.) The Mind as a ScientificObject, Oxford University Press 2005, pp. 293-316.

I. Summary:

(1) Theses:

a) The account of explanation offered in life sciences (especially in cognitive neuroscience)

takes the form of specification of mechanisms, wherein an overall activity of a system is

decomposed into subfunctions, and these are then localized to components of the system.

b) There is a neo-Gallean theme in cognitive neuroscience, where information gained from

neural studies often leads to fundamental revisions in functional decompositions of cognitive

performance.

(2) Overview:

Two of the Galls assumptions about the relation between the mind and the brain are present

in cognitive neuroscience. The first states that different mental processes are localized in

different parts of the brain. The second states that we can decompose each mental process into

faculties, each solely responsible for a mental trait. Both of these assumptions are related with

the main idea of Galls program, an idea that specific brain regions are responsible for

specific psychological capacities. However, for Gall (and some contemporary modularists like

Fodor) the decomposition of mind into faculties or modules comes prior to linking those

faculties with physical parts of the brain. It is a top-down approach to localization, where

modules are identified independently of their brain realization. A somewhat more interesting

strategy of decomposition of mental processes into modules and their localization in the brain

takes the form of an interplay between functional decomposition and neuroanatomical and

neurophysiological evidence.

This strategy is illustrated by a case study of decomposition and localization of attentional

mechanisms. Three models of attention are presented. The first is Broadbents (1958)

,,bottleneck model. According to this model, there is a limited cognitive resource, the

,,bottleneck, that stimulus information competes for. However, neural information lead to a

reconceptualization of attention. The second model, Posners (1992) ,,spotlight model, is

informed by this neural evidence. Posner experimented with subjects with brain lesions using

PET. It occured that victims of lesions with attentional deficits still have the capacity to

process information from every sensory modality, as well as semantic information. Theycould not, however, enhance this processing to the requisite degree when it is required for the

purposes of some task. Posner proposed that there is a system enhancing processing in

primary sensory areas (hence the ,,spotlight metaphor), which can be disabled with respect to

one of these areas. However, further neural evidence lead to another reconceptualization of

attention. Posner divided attention into a posterior system driven by visual stimuli and

anterior system driven by task-specific information. In a PET study, Corbetta et al.(1991)

examined the neural activation that accompanies performance on a visual search task

involving two frames representing an array of moving objects. The subjects were asked to

report if the two frames were the same or different with respect to color, shape etc. The

experiment suggested that for divided-attention and selective-attention conditions, non-

modality specific, linguistic instructions play a role in the control of attention. Therefore,according to the third model of attention, proposed by Desimone and Duncan (1995) and

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informed by new neural evidence, attentional selection involves biased competition among

different processing streams for the control of behavioral response.

II. Comments:

1) The case study of decomposition and localization of attention mechanism supports thesis(b). Different decompositions and localizations of this mechanism were heavily influenced by

evidence from neuroanatomy and neurophysiology. This lead to reconceptualizations of

attention in psychology. Furthermore, these reconceptualizations would not be possible

without the support from neuroscience. The above mentioned evolution of our understanding

of attention shows the advantage of the strategy of decomposition that is in interplay with

neuroscientific evidence over the strategy of decomposition that breaks down different mental

processes before linking them with specific parts of the brain.

2) The idea of decomposition of mental processes supports thesis (a). Cognitive scientists try

to brake down complex, intentional mental processes (such as language understanding) into

processes which can be described as mechanistic (such as attention). This idea is very similar

to Galls project od decomposition of mental functions into faculties.3) However, it is not clear whether complex, intentional mental functions can be explained

solely with specifications of different mechanisms, or modules. Mechanisms or modules can

be responsible only for very simple mental activity because they process only one kind of

information. By using different kinds of information from different sources, complex mental

functions seem to be qualitatively different from simple mechanisms, or modules.