Hemispheric specialization for spatial frequency ... - carole peyrin
1): The right TPJ would predominantly be involved in LFs analysis ... for spatial frequency processing when altering the picture frequency spectrum of natural.
Hemispheric specialization for spatial frequency processing in the analysis of natural scenes Carole PEYRIN, Alan CHAUVIN, Christian MARENDAZ and Sylvie CHOKRON Laboratory of Psychology & NeuroCognition (CNRS - UMR 5105) Pierre Mendès France University, Grenoble
Introduction
Left visual field
Right visual field
Results
The hemispheric asymmetry hypothesis
HFs 20 10
-10 -20 -30
-50
Spatial frequencies
400
390
380
370
40
LVF/RH CVF RVF/LH
30 20 10 0 -10 -20 -30 -40 -50
360
visula field of presentation
350
Figure1: Hemispheric specialization for spatial frequency processing
Research aims and hypotheses However, the hemispheric / TPJ hypothesis of spatial frequency processing has never empirically been demonstrated, but rather inferred from data obtained with the hierarchical form paradigm, without any explicit spatial frequency manipulation per se. The aims of the present research were:
(i)
to investigate, in healthy subjects, the hemispheric specialization for spatial frequency processing in natural scene perception, by altering the picture frequency spectrum.
(ii)
to examine whether the ‘precedence effect’ (the relative rapidity of LFs and HFs processing) depends on the visual field of scene presentation or not.
Experiment
410
-40
Right TPJ
HFs
LFs
30
0
Left TPJ
LFs
50
(ii)
420
Mean reaction time in ms
HFs
RH advantage
LFs
LH advantage
Data from psychophysics (Ginsburg, 1986), functional neuro-anatomy of magnocellular and parvocellular pathways (Van Essen & De Yoe, 1995), ultra-rapid categorizations in humans and monkeys (FabreThorpe & al., 1998) and simulation militate in favour of the idea that visual analysis starts with a parallel extraction of different elementary visual attributes at different spatial scales, with a coarse-to-fine processing design: A rapid extraction of low spatial frequencies (LFs) allows an initial categorization that is to be confirmed or refuted by the information conveyed by high spatial frequencies (HFs). Moreover, neuropsychological and functional imagery data have suggested that each hemisphere (at the level of the temporo-parietal junctions - TPJ) could play a key role in spatial frequency processing (Fig. 1): The right TPJ would predominantly be involved in LFs analysis and the left TPJ in HFs analysis (Ivry & Robertson, 1998).
(i)
40
HFs precedence LFs precedence
50
(i) Hemispheric specialization
LVF/RH
CVF
RVF/LH
Visual field of presentation
As expected, there was a significant interaction between the lateralized presentation (LVF and RVF) and the spatial frequency components of target scenes (LFs and HFs) [F(1;8)=10.57, p
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