First, let me say that I empathize with your opinions. Many of the articles using fMRI take tremendous liberties with the extent of theorizing they feel comfortable doing after finding a change in neuronal activity. But, probably some of this takes place simply because of the continued excitement over this technology. So I feel that there is ample room for your kind of objection, but I do not feel that Neuropsychology is the place for this kind of article. In my role as editor, I place a great deal of emphasis on the need to have "new" data in each manuscript that receives approval for publication and you don't seem to have this. If you could perform the experiment and show that varying conceptual and emotional aspects of the stimuli result in different patterns of activity and not difference amounts in different locations, then you would have an excellent chance of publication. But, just saying that it is a possibility without evidence is not sufficient, even though you may be perfectly correct. You need to fight this kind of overinterpretation of data with data of your own otherwise you will be boxing a shadow, arguing straw men, not proving your hypothesis. > > >Dear Laird Cermak, > >I would like to know if 'neuropsychology' is a suitable place for >submitting the text below. It is a response to an article that was >published by 'Current Biology', and it was rejected by 'Current Biology' >with extremely hostile and unfair reviews (You can access these in >http://human-brain.org/zeki-index.html). > >Thanks > >Yehouda Harpaz >yeh_harlequin.co.uk >http://human-brain.org > >-------------------------------------------------------------------- > >Functional Specialization in the visual Cortex? > > > > >Howard et al [1] showed their subjects three pairs of different kind of >stimuli, and use fMRI to measure the activity in their brain. Based on their >results, they conclude that there is "extraordinary degree of functional >specialization in the visual cortex". However, the conclusions do not follow >from their data. There are three major flaws in the logic of the argument that >Howard et al [1] use: > > > > 1) The authors ignore the higher level nature of the stimuli, i.e. their >conceptual and emotional significance. > > > > In higher level, the stimuli vary on many dimensions, e.g how > realistic they look, how interesting they are, how attractive they > are. Thus any difference in activity may be attributed to > differences in the significance of the stimuli, rather than to the > way they are processed. These effects must be controlled in some > way, before it can be concluded that the activity seen is wholly a > result of low-level processes. > > > >2) The authors assume that high differential activity is equivalent to >functional significance. > > > > > > Howard et al [1] measured differential metabolic activity, which > presumably also means differential neuronal activity. However, > differential neuronal activity does not entail functional > significance. In other words, the processing of the input is not > necessarily done where the highest differential activity is seen. > > > > The equivalence of differential activity and functional > significance is widely assumed, presumably because it simplifies > the analysis. However, there is no evidence for it at the > resolution in which Howard et al[1] present their data, and it is > logically implausible. This is because the bulk of the information > in the brain is not coded in level of activity (how many neurons > are active in a specific region), but in the pattern of activity > (which neurons are active and when). Thus processing input (or any > other process) means changes in pattern of activity, not level of > activity. Hence, regions where the processing take place does not > necessarily appear as peaks of differential activity. On the other > hand, peaks of differential activity can arise from other reasons, > including (a) high-level processes, (b) direct effect of the input > (rather than processing it), (c) completely irrelevant effects. > Thus the equivalence cannot be assumed, and must be supported by > evidence. > > > > > As the authors themselves point out, the area of differential > activity in their data seems to correlate with the size of the > visual input. On the other, it does not seem to correlate to the > amount of processing that is required for each stimulus. Thus the > data itself seems to hint that the differential activity in this > case is a direct result of the visual input, rather than anything > to do with processing it. > > > > >3) The authors regard localization as specialization. > > > `Specialization`, when applied to body organs, normally means some > physiological modification. Even if it will be shown that specific > kind of stimuli are processed in a specific region, it does not > show that this region is modified in a special way for processing > this kind of stimuli. Thus localization is not equivalent to > specialization. > > > > It can be claimed that localization is a weak form of > specialization, but this is a word game that would just lead to > confusion. Moreover, it is clearly not what Howard et al [1] mean, > as they claim in their conclusions that "there is an extraordinary > degree of functional specialization in the visual cortex". > > > > >The patterns of differential activity seen by Howard et al [1] do not match any patterns seen in >any other investigation, using any method, including, as the authors themselves say, their own >previous studies. This argues against specialization. As the argument for specialization is >invalid for any of the three flaws listed above, their data does not support specialization. > > > >In summary: The data presented by Howard et al[1] shows some degree of localization of >differential activity when subjects are presented with different stimuli. It does not show that this >localization is not a result of higher level effects, it does not show that this activity corresponds >to functional significance, and it does not show any evidence for specialization, as opposed to >localization. > > > >References: > > > >1. Howard RJ, Brammer I, Wright I, Woodruff PW, Bullmore ET, Zeki S: A direct >demonstration of functional specialization within motion-related visual >cortex of the human brain. Current Biology 1996, 6:1015-1019. > > > > > > >