The neural basis of implicit movements used in recognising hand shape

Lawrence M. Parsons, Peter T. Fox

Research output: Contribution to journalArticlepeer-review

133 Scopus citations


Psychophysical studies indicate that observers recognise the laterality of single, randomly oriented, visually presented hands by implicitly moving their left hand into the orientation of any left hand stimulus and their right hand into the orientation of right hand stimuli. Such data imply that lateralised somatic sensorimotor representations are engaged as one's action is mentally simulated to perceive stimulus handedness. This hypothesis was evaluated in a positron emission tomography study in which (mostly) right hands were tachistoscopically presented to the left visual field (right cerebral hemisphere) and vice versa. Exploiting known cerebral lateralisations, the design allowed the observation of a spatial dissociation of visual-field-lateralised and limb-lateralised neural activity. Although the primary somatosensory and motor cortices were not activated, strong regional cerebral blood flow increases (task minus rest) were observed in frontal (motor) and parietal (somatosensory) areas similar to those activated by actual and imagined movement. Limb-contralateral activations were in pre-supplementary motor area (pre-SMA), cerebellum, and opercular and superior frontal sulcal premotor cortex; these areas are implicated in a variety of motor and somatosensory functions. Activations in the dominant left hemisphere regardless of the limb were localised in SMA proper, superior premotor cortex, and inferior parietal cortex, areas involved in planning, guidance, and attention to motor performance. Activations in the nondominant right hemisphere for both limbs were present in dorsal superior premotor cortex, insula, superior parietal cortex, and occipitotemporal cortex; these areas underlie motor planning, high-level somatic representation, evaluation of visuospatial information, and representation of object/action identity. Overall, these data confirm or extend prior understanding of the distributed system of brain areas supporting motor imagery and the left-right judgement of body parts.

Original languageEnglish (US)
Pages (from-to)583-615
Number of pages33
JournalCognitive Neuropsychology
Issue number6-8
StatePublished - Sep 1 1998

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Experimental and Cognitive Psychology
  • Developmental and Educational Psychology
  • Arts and Humanities (miscellaneous)
  • Cognitive Neuroscience


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