Internally-represented space and its mirror-reversed image of the visuospatial representation: A possible association.
The cognitive capacity for number representation is thought to be a functional isomorphism of space representation. Numbers are represented in a left-to-right-oriented mental number line and hemispatial neglect patients consistently demonstrate rightward midline shift of visuospace, the internal space and number representation. However, patients with pathologic pain in one limb showed a negative correlation between midline shift of the visuospace and number representation. The purpose of the present study is to ascertain whether such dissociation in accessing space and number representation is observed in another neuropathic pain condition, and then to propose a theoretical model regarding an intimate relationship between visuospace and internal space representations. Using patients with deafferentation pain caused by a nerve lesion in a limb, we investigated whether number representation is closely linked to space representation by evaluating visual subjective body-midline judgments in dark and light conditions (egocentric- and allocentric-spaces, respectively). We also used a number-interval-bisection task to analyze this question. All of the patients perceived allocentric-space accurately. Respective patients showed perceptual shifts in egocentric-space and number representation, however they did not demonstrate any trend of the shifted-direction. Direct comparison revealed that number representation is negatively correlated with not allocentric-space but egocentric-space: a leftward midline-shift of egocentric-space was linked with a rightward midline-shift of number bisection, and vice-versa. Internally-represented space demonstrated a mirror-reversed image of the visuospatial representation, similar to our previous finding. To explain the inverted representation, we can propose a theoretical model that spacing between mentally-aligned numbers in a left-to-right sequential line is anisometric.
Department of Pain and Palliative Medicine, The University of Tokyo Hospital, Tokyo, Japan. Electronic address: sumitanim-ane@h.u-tokyo.ac.jp.
Masahiko
M
Sumitani
Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, Kobe, Japan.
Masaya
M
Misaki
Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.
Shin-ichiro
S
Kumagaya
Department of Rehabilitation Medicine, The University of Tokyo Hospital, Tokyo, Japan.
Arito
A
Yozu
Department of Rehabilitation Medicine, The University of Tokyo Hospital, Tokyo, Japan.
Yuko
Y
Otake
Neurorehabilitation Research Center, Kio University, Nara, Japan.
Michihiro
M
Osumi
Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, Kobe, Japan.
Satoru
S
Miyauchi
D000293:Adolescent; D000328:Adult; D000368:Aged; D000671:Amputation, Surgical; D001917:Brachial Plexus / Q000503:physiopathology; D003071:Cognition; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008160:Lumbosacral Plexus / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009369:Neoplasms / Q000150:complications / Q000503:physiopathology; D009437:Neuralgia / Q000503:physiopathology; D010468:Perceptual Disorders / Q000209:etiology* / Q000503:physiopathology*; D059348:Peripheral Nerve Injuries / Q000150:complications / Q000503:physiopathology; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D020196:Trauma, Nervous System / Q000503:physiopathology; D014785:Vision, Ocular / Q000502:physiology*; D014947:Wounds and Injuries / Q000150:complications / Q000503:physiopathology