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Electronic Letters to:
- Neurobiology of Disease:
Antígona Martínez, Steven A. Hillyard, Elisa C. Dias, Donald J. Hagler, Jr, Pamela D. Butler, David N. Guilfoyle, Maria Jalbrzikowski, Gail Silipo, and Daniel C. Javitt- Magnocellular Pathway Impairment in Schizophrenia: Evidence from Functional Magnetic Resonance Imaging
J. Neurosci. 2008; 28: 7492-7500[Abstract] [Full text] [PDF]
eLetters: Submit a response to this article
Electronic letters published:
Spatial frequency and magnocellular sensitivity in schizophrenia
- John R Skoyles, Bernt Skottun (6 August 2008)
Spatial frequency and magnocellular sensitivity in schizophrenia 6 August 2008 
John R Skoyles,
Research Fellow
CoMPLEX, University College London, 4 Stephenson Way, London, NW1 2HE,
Bernt SkottunSend letter to journal:
Re: Spatial frequency and magnocellular sensitivity in schizophrenia
j.skoyles{at}ucl.ac.uk John R Skoyles, et al.
Martinez et al. (2008) used fMRI to study the visual cortex of schizophrenic subjects and controls. They interpreted their results as evidence for a magnocellular deficit in the former. This conclusion is, however, not supported by the evidence from stereoacuity (Skottun and Skoyles, 2008a), visual masking (Skottun and Skoyles, 2008c), postmortem anatomy of the LGN (Selemon and Begovic, 2007; Dorph-Petersen et al., 2008) and the overwhelming majority of contrast sensitivity studies (Skottun and Skoyles, 2007).
Martinez et al. (2008) categorized the results into four different spatial frequency ranges and found the number of voxels preferring low spatial frequencies (i.e. 0.2 -1.4 c/deg) to be much smaller in the schizophrenic subjects than in the controls. However, using spatial frequency to separate magno- and parvocellular responses at supra- threshold contrasts is difficult (Skottun and Skoyles, 2008) since single cell recordings have found the optimal frequencies and cut-off frequencies of magno- and parvocellular neurons to be quite similar (Spear et al., 1994) particularly when eccentricity is taken account of (Blakemore and Vital-Durand, 1986). Given these facts, and the contrast levels used, it is not clear how to understand the findings of Martinez et al. That is to say, it is not clear what outcome one would predict for a magnocellular deficit in this experiment and how this would differ from the prediction for a parvocellular or a cortical deficit.
References
Blakemore C, Vital-Durand F (1986) Organization and post-natal development of the monkey's lateral geniculate nucleus. J Physiol (Lond) 380:453-491.
Dorph-Petersen KA, Caric D, Saghafi R, Zhang W, Sampson AR, Lewis DA (2008) Volume and neuron number of the lateral geniculate nucleus in schizophrenia and mood disorders. Acta Neuropathol. In press.
Martinez A, Hillyard SA, Dias EC, Hagler Jr DJ, Butler PD, Guilfoyle DN, Jalbrzikowski M, Silipo G, Javitt DC (2008) Magnocellular pathway impairment in schizophrenia: evidence from functional magnetic resonance imaging. J Neurosci 28:7492-7500.
Selemon LD, Begovic A (2007) Stereologic analysis of the lateral geniculate nucleus of the thalamus in normal and schizophrenic subjects. Psychiatry Res 151:1-10.
Skottun BC, Skoyles JR (2007) Contrast sensitivity and magnocellular functioning in schizophrenia. Vision Res 47:2923-2933.
Skottun BC, Skoyles JR (2008a) Stereopsis and magnocellular sensitivity in schizophrenia. World J Biol Psychiat. In press.
Skottun BC, Skoyles JR (2008b) Spatial frequency and the magno- parvocellular distinction--some remarks. Neuro-Ophthalmology. In press.
Skottun BC, Skoyles JR (2008c) Are masking abnormalities in schizophrenia limited to backward masking? Int J Neurosci. In press.
Spear PD, Moore RJ, Kim CB, Xue J-T, Tumosa N (1994) Effects of aging on the primate visual system: spatial and temporal processing by lateral geniculate neurons in young adult and old rhesus monkeys. J Neurophysiol 72:402--420.
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