Animals recover but plant life knowledge is still impaired 10 years after herpetic encephalitis: the long-term follow-up of a patient

Abstract

In this study we report the long-term follow-up of EA, a patient originally affected by a disproportionate semantic impairment of biological categories due to herpetic encephalitis. After 10 years, EA still presented a biological categories semantic impairment, but his deficit had become minimal for animals while it remained considerably severe for fruit and vegetables, without any evolution from the original level of impairment. The eventual discrepancy between the two subsets of biological categories was statistically significant at word–picture matching and verbal semantic probes (and could not be explained by nuisance variables), but not significant at picture naming due to an associated lexical impairment that, besides plant life items, also affected animals and artefact stimuli.

The mean male familiarity for the 10 vegetable stimuli was 2.08 (SD = 0.52, range 1.46–3.05), that for the 10 fruit stimuli was 2.31 (SD = 0.25, range 1.84–2.68), and that for the 10 animal stimuli was 1.44 (SD = 0.24, range 1.18–1.97).Vegetable stimuli were celery, corn, onion, pepper, artichoke, asparagus, mushroom, carrot, lettuce, tomato. Fruit stimuli were banana, watermelon, pineapple, cherry, pear, strawberry, lemon, apple, grapes, orange. Animal stimuli were giraffe, camel, ostrich, frog, swan, caterpillar, cow, rooster, butterfly, mouse. The list of the 60 stimuli and all the familiarity values are reported by Albanese et al. (2000). The values of word frequency (for the Italian language), prototypicality, image agreement, and visual complexity for all the stimuli are eported in Laiacona and Capitani (2001).

Our recovery data corroborate the notion that biological categories should be further fractionated, and we comment on the suitability of different accounts of category specificity to accommodate such findings. We discuss our case against the background of other cases reported in the literature and the current models of organisation of the semantic system, bringing to light some interesting consistencies concerning patients whose semantic impairment disproportionately affects the categories of fruit and vegetables.

Acknowledgement

We are grateful to EA for his generous help and patience. Rosemary Allpress revised the English text. Nadia Allamano and Lorena Lorenzi assisted with the language examination. This project was partly supported by MIUR grants to EC.

Notes

The mean male familiarity for the 10 vegetable stimuli was 2.08 (SD = 0.52, range 1.46–3.05), that for the 10 fruit stimuli was 2.31 (SD = 0.25, range 1.84–2.68), and that for the 10 animal stimuli was 1.44 (SD = 0.24, range 1.18–1.97).Vegetable stimuli were celery, corn, onion, pepper, artichoke, asparagus, mushroom, carrot, lettuce, tomato. Fruit stimuli were banana, watermelon, pineapple, cherry, pear, strawberry, lemon, apple, grapes, orange. Animal stimuli were giraffe, camel, ostrich, frog, swan, caterpillar, cow, rooster, butterfly, mouse. The list of the 60 stimuli and all the familiarity values are reported by Albanese et al. (2000). The values of word frequency (for the Italian language), prototypicality, image agreement, and visual complexity for all the stimuli are eported in Laiacona and Capitani (2001).

For this set of stimuli the ratings of estimated age of acquisition of fruit was 3.47, that of vegetables was 4.63, and that of animals was 3.98 (Nisi, Longoni, & Snodgrass, 2000).

Directly estimated values of age of acquisition were not available for the stimuli of our battery. On the other hand, in other material, age of acquisition estimated from adult ratings showed a correlation with true age of acquisition (r = .85, Morrison, Chappell, & Ellis, 1997), which is similar to the correlation between the latter variable and familiarity (−.80, Burani, Barca, & Arduino, 2001). On this basis, it seems not particularly specific. Anyway, for the stimuli in our battery, fruit shows the lowest age of acquisition and vegetables show the highest, with animals ranking in between. The ratings by Nisi et al. (2000) were 3.26, 4.71, and 4.09 for fruit, vegetables, and animals respectively. Because fruit and vegetables show a similar level of impairment, age of acquisition is unable to account for the discrepancy between animals and plant life in this case.

Follow-up data were reported for two other patients affected by biological categories impairment, HJA and JBR. Case HJA was examined more than 10 years after a left posterior cerebral artery stroke by Riddoch, Humphreys, Gannon, Blott, and Jones (1999), but his deficit was prevailingly agnosic, and at the outset he performed well on probe questions when the stimuli were presented auditorily, so we cannot study recovery in this case (on the contrary, a deterioration in some tasks was observed). Case JBR (Warrington & Shallice, 1984) was examined by Funnell and De Mornay Davies (1996) many years after herpes encephalitis, which had caused a bilateral temporal damage; no direct evaluation of recovery was presented, but JBR was still substantially impaired in the last examination when asked to verify properties concerning biological stimuli (animals and fruit/vegetables) that he was unable to name.

Even if IOC originally may have had some deficits with fruit and vegetables in a word-to-picture verification task, as reported by Shelton, Fouch, and Caramazza (1998), a semantic impairment was not confirmed on the exhaustive examination reported by Miceli et al. (2001). In the latter paper, separate data for the verbally assessed semantic knowledge of fruit and vegetables is not reported and was communicated to us by courtesy of Professor Gabriele Miceli.