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.
Two of the Gall’s 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 Gall’s 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 Broadbent’s (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, Posner’s (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. They could 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 informed by new neural evidence, attentional selection involves biased competition among different processing streams for the control of behavioral response.
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 Gall’s 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.
Short review: Zawidzki, T., Bechtel, W. (2005), ,,Gall’s Legacy Revisited: Decomposition and Localization in Cognitive Neuroscience”, [in:] Erneling, Ch., Johnson, D. (eds.) The Mind as a Scientific Object, Oxford: Oxford University Press, pp. 293-316.