MadSci Network: Neuroscience
Query:

Re: what is human reaction time due to?

Date: Fri Mar 2 14:27:52 2001
Posted By: Eric Tardif, Post-doc/Fellow, Institut de Physiologie, Université de Lausanne
Area of science: Neuroscience
ID: 982785622.Ns
Message:

Dear Asim,

You can estimate reaction times by asking, for example, a subject to press 
a level when he/she sees a light and to do it as fast as possible. In this 
situation, the light stimulates receptors in the retina, producing 
impulses in the optic nerve and transmitting information to visual areas 
of the brain. From these areas, information is likely to be transferred to 
motor areas of the brain which then send efferents to the motoneurones of 
the spinal chord, which in turn send impulses to the muscles. All this 
takes some time, which is called « reaction time ». When testing reaction 
time in a reflex behaviour (ex. knee jerk), one will find that it is much 
faster : this is because the sensory nerves that are stimulated when 
tapping the tendon send the information directly to the motoneurons of the 
spinal chord. Similarly, when a nociceptive stimulus (ex. electric shock) 
is applied, the limb is moved without the control of the brain. However, 
the nociceptive reflex is somewhat slower that the knee jerk, in part 
because the nociceptive fibres are slower but nevertheless, the reaction 
time is faster than auditory or visual. The auditory reaction time is also 
usually faster than the visual, although this may be relative to the 
stimuli used to assess the reaction time. That is possibly due in part to 
the differences between auditory and visual receptors ; the visual 
involve more chemical reactions whereas the auditory is mechanical. 
Moreover, sensory reaction time also depends on the attentional state and 
on training. If you introduce a « pre-signal » that warns the subject that 
the actual signal will arrive in, say, a second, this will diminish the 
reaction time. Finally, it worth mentioning that there are great inter-
individual differences.

I hope this helps !
Eric




Current Queue | Current Queue for Neuroscience | Neuroscience archives

Try the links in the MadSci Library for more information on Neuroscience.



MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-2001. All rights reserved.