David J. Howard

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Brain activity during reading tasks was investigated using PET. The aim was to account for differences in the results of two previous studies [those of Petersen et al. (Science 1990; 249: 1041-4) and Howard et al. (Brain 1992; 115: 1769-82)] by systematically varying the type of reading task and the exposure duration of the word stimuli. Both variables(More)
Many patients with progressive fluent aphasia present with poor verbal comprehension and profound word-finding difficulties in the context of much better picture comprehension and object use. The Japanese term Gogi (literally "word-meaning") aphasia matches this behavioural pattern. The alternative label of semantic dementia is most often used for these(More)
Positron emission tomography was used to investigate changes in regional cerebral blood flow (rCBF) in neurologically normal subjects during word reading and word repetition. The blood flow in these conditions was compared with control conditions where subjects were presented with stimuli of comparable auditory and visual complexity to real words and said(More)
The neural systems involved in hearing and repeating single words were investigated in a series of experiments using PET. Neuropsychological and psycholinguistic studies implicate the involvement of posterior and anterior left perisylvian regions (Wernicke's and Broca's areas). Although previous functional neuroimaging studies have consistently shown(More)
Age of acquisition and imageability ratings were collected for 2,645 words, including 892 verbs and 213 function words. Words that were ambiguous as to grammatical category were disambiguated: Verbs were shown in their infinitival form, and nouns (where appropriate) were preceded by the indefinite article (such as to crack and a crack). Subjects were(More)
We report an experiment in which subjects named 120 pictures, consisting of series of five pictures drawn from each of 24 semantic categories (and intermixed with 45 fillers). The number of intervening trials (lag) between successive presentations of members of the same category varied from two to eight. Subjects' naming latencies were slowed by 30 ms for(More)
Semantic category effects, such as difficulties in naming animate things relative to inanimate objects, have been explained in terms of the relative weightings of perceptual and functional features within the semantic representations of these concepts. We argue that grammatical category deficits, such as difficulties in naming nouns relative to verbs, can(More)
Processing of speech is obligatory. Thus, during normal speech comprehension, the listener is aware of the overall meaning of the speaker's utterance without the need to direct attention to individual linguistic and paralinguistic (intonational, prosodic, etc.) features contained within the speech signal. However, most functional neuroimaging studies of(More)
Background: Impairments of word retrieval and production are a common and distressing feature of aphasia, and much clinical time is devoted to attempts at their remediation. There are now many research papers devoted to case studies examining treatments for wordretrieval impairments using a wide range of tasks with individuals who have varying levels of(More)
The relationship between activity within the human auditory cortices and the presentation rate of heard words was investigated by measuring changes in regional cerebral blood flow with positron emission tomography. We demonstrate that in the primary auditory cortices and middle regions of the superior temporal gyri there is a linear relationship between the(More)