Concepts and categories: a cognitive neuropsychological perspective

Abstract

One of the most provocative and exciting issues in cognitive science is how neural specificity for semantic categories of common objects arises in the functional architecture of the brain. More than two decades of research on the neuropsychological phenomenon of category-specific semantic deficits has generated detailed claims about the organization and representation of conceptual knowledge. More recently, researchers have sought to test hypotheses developed on the basis of neuropsychological evidence with functional imaging. From those two fields, the empirical generalization emerges that object domain and sensory modality jointly constrain the organization of knowledge in the brain. At the same time, research within the embodied cognition framework has highlighted the need to articulate how information is communicated between the sensory and motor systems, and processes that represent and generalize abstract information. Those developments point toward a new approach for understanding category specificity in terms of the coordinated influences of diverse regions and cognitive systems.

Figure 1

Representative picture naming performance of patients with category-specific semantic deficits for (a) living animate things, (b) fruit/vegetables, (c) conspecifics, and (d) nonliving.

Figure 2

Relation between impairments for a type or modality of knowledge and category-specific semantic deficits. These data show that (a) category-specific semantic impairments are associated with impairments for all types of knowledge about the impaired category, (b) differential impairments for visual/perceptual knowledge can be associated with (if anything) a disproportionate impairment for nonliving things compared to living things, and (c) selective impairment for knowledge of object color is not associated with a corresponding disproportionate deficit for fruit/vegetables. Data for EW from Caramazza & Shelton 1998; GR and FM from Laiacona et al. 1993; DB from Lambon Ralph et al. 1998; and RC from Moss et al. 1998.

Figure 3

Category-specific patterns of blood oxygen–level dependent (BOLD) responses in the healthy brain. A network of regions that are differentially activated for living animate things is in red; a network of regions that are differentially activated for nonliving things is in blue. Data from Chao et al. (2002); graphics provided by Alex Martin.

Figure 4

Relation between knowledge of how to manipulate tools and other knowledge of tools. (a) Ochipa and colleagues (1989) reported a patient with a severe impairment for manipulating objects but relatively preserved naming of the same objects. (b) A multiple single-case study of unselected unilateral stroke patients asked patients to use and identify the same set of objects (Negri et al. 2007). Performance of the patients is plotted as t values (Crawford & Garthwaite 2006) compared to control (n = 25) performance. (c) Lesions to parietal cortex, in the context of lesions to lateral temporal and frontal regions, can be instrumental in modulating the relationship between performance in object identification and object use, at the group level (see Mahon et al. 2007, figure 7, for details and lesion overlap analyses). Each circle in the plots represents the performance of a single patient in object identification and object use. The 95% confidence intervals around the regression lines are shown. Reproduced with permission from Mahon and colleagues (2007). (d) Patient WC (Buxbaum et al. 2000) was impaired for matching pictures based on how objects are manipulated but was spared for matching pictures based on the function of the objects.