Are Semantic Systems Separately Represented in the Brain? The Case of Living Category Impairment

Abstract

Following herpes encephalitis, a patient showed impaired knowledge of animals, fruits and vegetables, flowers and food (so called living things categories), whatever the modality in which stimuli were presented and responses were given. A series of experiments showed that the deficit specifically affected the ability to retrieve the perceptual features of the living stimuli defining their shape, while knowledge of their functional-encyclopedic properties was preserved. The patient had no problems with man-made objects, except when the recall of their colour, or the identification of their sound was requested. It is argued that the retrieval of the perceptual features was potentially disrupted for every type of category, but that the block was compensated for man-made objects, because the close correspondence between shape and function that characterises them provided an alternative route to access their structured form representations. On this account, the selective deficit for living categories seems contingent on the interaction between an overall cognitive impairment--the deficit in retrieving perceptual features--and some intrinsic properties of the stimulus--the factors that have modelled its form--and cannot be taken as evidence that semantic systems are allotted to separate cerebral areas.

When Leopards Lose Their Spots: Knowledge of Visual Properties in Category-specific Deficits for Living Things

“…Unfortunately our materials were not designed to allow systematic comparisons among relevant types of perceptual property for SE. Our data also impose further constraints on the details of a distributed account, over and above those suggested by De Renzi and Lucchelli (1994). Specifically, the inter-relations among visual and non-visual properties must allow the visual properties of non-living things to be activated rapidly and automatically, such that they can support normal on-line priming in situations where controlled inference processes cannot operate.…”

“…This hypothesis has gained support from several studies of patients with category-specific deficits for living things, who have all demonstrated the predicted pattern of a greater problem for visual than nonvisual semantic properties (De Renzi & Lucchelli, 1994;Farah, Hammond, Mehta & Ratcliff, 1989;Hart & Gordon, 1992;Sartori & Job, 1988;Sartori et al, 1993a;Sartori, Job, Miozzo, Zago, & Marchiori, 1993b;Silveri & Gainotti, 1988). There is also converging evidence from studies of unimpaired subjects that visual/perceptual properties are particularly important for the identification of living things (e.g.…”

“…However, one recent study does address this issue directly. De Renzi and Lucchelli (1994) present the case of Felicia, who is recovering from HSE infection and who shows the typical pattern of a semantic deficit that is more marked for living things than non-living things. Felicia also showed a specific problem for visual properties that was apparently confined to the category of living things.…”

The fur of the crocodile and the mooing sheep: A study of a patient with a category-specific impairment for biological things

“…Several cases of category-specific deficit for biological things also displayed an important impairment in drawing affected category exemplars from memory (e.g., De Renzi & Lucchelli, 1994;Forde et al, 1997;Sartori & Job, 1988;Sheridan & Humphreys, 1993). Two such tests were presented to ER: memory-drawing and drawing completion.…”

“…However, the expression category-specific semantic impairment for living things must be considered as a shorthand "as not all the affected categories are living and not all living categories are affected" (Gainotti, Silveri, Daniele, & Giustolisi, 1995, p. 256). In fact, several studies have shown that in patients with a category-specific impairment for living things, food and, sometimes, musical instruments are also impaired, whereas body parts are often spared (e.g., Basso et al, 1988;De Renzi & Lucchelli, 1994;Forde et al, 1997;Sartori & Job, 1988;Sheridan & Humphreys, 1993;Silveri & Gainotti, 1988;Sirigu et al, 1991;Warrington & Shallice, 1984).…”