Hi there! Altered visuomotor processing speeds may be an intrinsic feature of schizophrenia. But did you consider that treatment with neuroleptic agents can acutely or chronically interfere with such functions and interfere with your measurements?

Hi! Thank you for this quick answer. Actually we did and collected informations about chronicity and medication (which were converted into Chlorpromazine equivalents) but medication failed to correlate significantly with these RTs values. In your opinion, altered visuomotor processing could lead to low RTs?

Yes, this would not surprise me and should specifically affect tests like the trail making test (TMT). It is somewhat confusing, but a LOWER reaction time indicates a BETTER performance. It is interesting to learn, that you could not detect any correlation between chronic medicationand RT. I would have expected the opposite (but I am primarily working on the molecular background of schizophrenia. So I am far from being an expert in psychometrics!) 

Asking for clarification: Low RT means quicker reaction than high RT?

Hi Stephen, yes indeed. In this case, they're actually "too quick"; it rather looks like impuslivity or lack of inhibition than the "normal" (even minimal) time took to react to a visual stimulus (but it is to note that the protocol is not made to assess inhibition processes)

Have a look at the work of  the Heart maths institute, psychotic and psychic are very closely linked. Heart maths studies involved head and heart monitors on subjects who were shown random photos on a screen. Interestingly the heart reacted to shock photos before the brain did and in some individuals a reaction happened seconds before the photo appeared. Science seems to be scared of investigating the possibility of intelligent interaction with the electromagnetic field that surround us. This could indeed be the very survival mechanism to adverse stress that produces the anomalous experiences we call psychosis. 

Anecdote, which is what this non-academic, non-clinician mental health worker can provider here: I once met with a young woman who had very prominent negative symptoms, and many questions she could not answer at all, due to thought blocking. But when she did know an answer, she was very eager to provide it and jumped right in. So one thing you might go back and do, if possible, is see what the baseline functioning of your test group was in terms of negative symptoms, and whether your test is just one of the few things in their day they fell they can do correctly and without getting into trouble, so they rush to answer?

Another query I would have, given than persons diagnosed with schizophrenia sometimes have schizoaffective or bipolar with psychotic features, is whether some mania was helping them answer quickly and confidently, particularly if you did your testing around the April-May or October-November.

Were the low RTs associated with more or less accurate responses compared to the controls?

Thank you Theresa, Heather and Mark for sharing your point of view, that really helps me going further in my reflexion. Stephen it actually depends on what I consider to be an accurate response and in this case it is really problematic. Let me explain myself: participants see a serie of stimuli in which one is the target and they should press a command as soon as they see it (they have 1500 ms to do so, any answer before 0 ms is considered as an anticipation and any answer occurring after 1500 ms is an omission). The task is built so that some series  contain a grammar that predicts the immediate appearance of the target, some other are just random. Some authors using this type of protocol  before consider that a correct response is any response occurring between 150 and 1500 ms, this first value (150) refers to the minimal time took to identify a visual stimulus I guess. In controls, there's actually no problem with that: it is pretty uncommon to find very low RTs (under 150 ms) in their protocol while in people with schizophrenia, there are plenty of it. And as I was saying, not only when the aforementioned grammar help them predicting the target appearance but even in random series. So you can see the problem: shall we continue to use "normal values" to define what is an accurate response (and half of my population is consenquently very inaccurate)? And even if these responses are actually inaccurate I really want to understand which specific processes could lead to it because they are too much frequent to just deny that such specific processes exist. 

Hi Romina,

just to follow up on Stephen Moores' comment, I think he has a good point. In reaction time tasks, there is often a speed/accuracy trade-off. For example, if patients pay little attention to the stimuli, they can be very fast, but as a consequence make a lot of errors. Do you have data on whether patients responded more often to non-target stimuli (i.e., errors) than controls? If so, you could correlate this to RT's, would be interesting. 

Schizophrenis is a psychosis that has a main characteristic distortions of thinking and perception, inappropriate and blunted affect, cognitive deficits, delusions, hallucinations, ambivalence and disturbance of volition. Because of this disorganization of ego, cognitive processes such as memory, attention and abstract reasoning and enforcement are disadvantaged.

Anouk is exactly correct with respect to the speed/accuracy trade-off. Another approach would be to examine RTs only for "on-target" responses, although if accuracy is at or near chance levels, then this metric wouldn't be so reliable.

Hi Anouk and Andrew, yes indeed, they are less accurate stricto sensu; namely they show  significantly more omissions than controls but globally not more or less anticipations. That would mean indeed that they pay less attention to a larger extent. I just would have expected that less attention would have lead to higher RTs but your idea seem congruent.

Dear Romina:

I am not engaged in schizophrenia etc, but in psychophysics.

Some answers (Stephen, Anouk, Andrew) addressed the accuracy already. Andrew specified the point: responses to targets and responses to non-targets.

As I understood from your explanation, every sequence in your experiment contains a target, but targets are presented either without supporting grammer or with supporting grammer. Thus, the criterium RT

Is it the very low reaction time by drug free patients? Or it is influenced with neuroleptica...

Thank you Werner. I could not work on that over the past two weeks but will try to lead those following your different ideas and will keep you informed about the results.

Nikola: all the patients were under neuroleptic treatment, the doses have been controlled in chlorpromazine equivalents and does not correlate with those low RTs so far.