A follow-up study was undertaken in order to investigate the outcome of recovery from right and left hemiplegia on simple motor function and activities of daily living. The role of concomitant neurophysiological deficits was also investigated. The main results indicate that after six months from onset, left hemiplegics show a lesser degree of improvement in independence and social adjustment coupled with a tendency to a poorer recovery of motor function than the corresponding group of right hemiplegics. Unilateral spatial neglect, which is more frequent and severe in the group of left hemiplegics, seems to be crucial in hampering their performance.

A patient is described who is affected by an inability to recall and use 'arithmetical facts' of one-digit multiplications and divisions. This loss contrasts with the preservation of a wide set of complex notions that the patient exploits in order to overcome his deficit and get the right result. This observation helps in isolating and describing an important component of arithmetical long-term memory that is not overlearnt and the functioning of which is not automatic or mechanistic. An account of such a component is lacking in models of arithmetic currently referred to in cognitive neuropsychology. In a remediation study, performed over several weeks, the effect of training was selective for each single arithmetical fact: not even skills with multiplication complements (e.g. 6 x 3, 3 x 6) fully benefited from the rehabilitation of a specific fact. This suggests that the storage format of each fact is independent from that of other facts.

In this study we investigated the acalculic condition of a patient, C.G., with the classical signs of Gerstmann's Syndrome: finger agnosia; right-left disorientation; a profound agraphia (but with an equally profound alexia) and a remarkably dense acalculia. Using a series of number processing and number knowledge tasks, a selective impairment for numbers was demonstrated. Within the category of numbers C.G. showed a largely preserved ability to deal with numbers below 4, in all tasks and in all modalities, while she was totally unable to deal with numbers above 4. The consistency of responses and the ineffectiveness of cueing indicated that numbers above 4 were lost, rather than hard to access. Further testing showed that this impairment did not result from a more general semantic memory problem, a difficulty in understanding quantities or a deficit in reasoning abilities thought to underlie the concept of numbers. Difficulty with some other ordinal structures was also present, but appeared unrelated to those affecting numbers.

No abstract

A brain-damaged patient is described whose pattern of performance provides insight into both the functional mechanisms and the neural structures involved in visual mental imagery. The patient became severely agnosic, alexic, achromatopsic and prosopagnosic following bilateral brain lesions in the temporo-occipital cortex. However, her mental imagery for the same visual entities that she could not perceive was perfectly preserved. This clear-cut dissociation held across all the major domains of high-level vision: object recognition, reading, colour and face processing. Our findings, together with other reports on domain-specific dissociations and functional brain imaging studies, provide evidence to support the view that visual perception and visual mental imagery are subserved by independent functional mechanisms, which do not share the same cortical implementation. In particular, our results suggest that mental imagery abilities need not be mediated by early visual cortices.