Dear Tipsters Susan Blackmore recently published in june 03 book an "Introduction to Conciousness" http://www.susanblackmore.co.uk/journalism/ns02.htm Its a great read Alexia Elliott ------------------------------------------------------------------------- FIGHT BACK AGAINST SPAM! Download Spam Inspector, the Award Winning Anti-Spam Filter http://mail.giantcompany.com
----- Original Message ----- From: "jpuente" <[EMAIL PROTECTED]> To: "Teaching in the Psychological Sciences" <[EMAIL PROTECTED]> Sent: Saturday, September 20, 2003 9:44 PM Subject: RE: Split Brain Dilemma AND automaticity Dear Stephen, I appreciate your thorough response to my split brain dilemna. Your answer gave me some ideas, as well. When I looked back at Carlson's "Physiology of Behavior" (6th ed., 1998), he speaks confidently of the split brain patient being able to comprehend verbal instruction to the right hemisphere. I thought that, perhaps, this might not be so surprising given that neural networks would (presumably) form in both hemispheres in response to auditory inputs (audition goes to the hemisphere on the side that it enters, right? Just like olfaction?). What are your thoughts on this? In addition, I have been intrigued by the idea that we can only "know" something (i.e. be conscious of it) when the information reaches the centers within our brain responsible for verbal communication. I wonder if this can, in some way, lend support to the idea that our conscious will is merely an afterthought of the "clockwork mechanisms" of the brain. This is definitely a tangent to the split brain topic we started on, but I am very interested in empirical studies of free will and automaticity. One study that I find rather convincing in support of automaticity is Libet's (1985) study, in which he tests whether intentions precede brain activity to an action or vice versa. It's always fun discussing this one with students, by asking them "If I were to ask you to guess whether the brain activity that happens when you decide to move your finger happens before or after you "want" to move your finger, what would you think?" .so, anyway, perhaps the split brain patients' abilities to know things unconsciously when the information is in their right hemisphere also lends support to automaticity arguments? Do you or any of the rest of the group have thoughts on this topic? [btw, the reference for the Libet study: Libet (1985). Unconscious cerebral initiative and the role of conscious will in voluntary action. Behavioral & Brain Sciences. Vol 8(4), Dec 1985, 529-566.] Best, JP >>===== Original Message From "Teaching in the Psychological Sciences" ><[EMAIL PROTECTED]> ===== >On 18 Sep 2003, jpuente wrote: > >> I have an interesting question posed by one of my students re: the >> capabilities of a split brain patient. >> >> <snip> >> The dilemna: >> In a video demonstration, after seeing the word car in his left visual >> field, a split brain patient was able to draw, with left hand, a >> picture of a car. This demonstration implies that the right >> hemisphere has the ability to allow a splitbrain person to understand >> language (he read the word and drew a picture of it), but not provide >> speaking capabilities. Does this mean that Wernicke's area is only >> important for speach comprehension (not other language comprehension)? >> And, if so, what other areas mediate language comprehension? >> > >Good question. I'd just suggest that it not be limited to Wernicke's >area but phrased more generally: Does the right hemisphere have >language ability, in particular the ability to read? > >There would be no problem if the patient had his speech represented >in the right hemisphere. And yes, some people do have bilateral or >right-hemisphere language representation, but these are mostly >lefties, and they're still a minority. One recent fMRI imaging study >(Pujol et al, 1999) found that 76% of left-handers had left-side only >language representation and this figure went up to 96% in right- >handers. On the other hand, split-brainers were split because of >severe and long-standing brain dysfunction, which may have >compromised the left hemisphere, promoting a shift to right- >hemisphere representation of language. In fact, Springer et al >(1999), in another fMRI study, found (in r-handers), that 94% of >normals were left-dominant for language but only 78% of an epilepsy >group. So the percentage of patients with right-side language >representation is probably greater in split-brain cases than in >normals. > >But the patient shown in the video may not have been one of these. So >I checked textbooks. Carlson, in his 8th edition _Physiology of >Behavior (2004), gives little space to split-brain, and says flatly >that the right hemisphere can't read (p. 6). But other sources show >that a standard testing technique is to present different words to >the different hemispheres and observe different responses (as in the >video). As not all of these people are likely to be right-hemisphere >dominant for language, it suggests that the right hemisphere must be >able to read and understand individual words. This is what Pinel, in >_Biopsychology, 5th ed_ (2003) says: > >"In most split-brain patients, the left hemisphere is dominant for >language, but the right hemisphere can understand many spoken or >written words and simple sentences (see Baynes & Gazzaniga, 1997; >Zaidel, 1987)...although there is considerable variability among >split-brain patients in the performance of their right hemisphere on >tests of language comprehension (Gazzaniga, 1998), the language >abilities of their right hemispheres tend to be comparable to those >of a preschool child" [but one who can read, apparently]. > >Just to be sure, I also tried Kandel, _Essentials of Neural Science_ >(1995), and his take is similar. He says: > >"We speak after all, as Broca first illustrated, with our left >hemisphere. Nevertheless, the right hemisphere may be capable of a >primitive understanding of language. For example, some words >projected to the right hemisphere can be read and understood. If the >letters D-O-G are flashed in the left visual field (the right >hemisphere) the patient selects a model of a dog with his left hand. >More complicated verbal inputs to the right hemisphere, such as >comands, are comprehended poorly. Although the right hemisphere >appears almost totally incapable of language _output_, it does seem >able to process simple linguistic _inputs_.": (p. 356) > >So it's another example that the left-right dichotomy (this side of >the brain does this; that side does that) is too simple a description >for what really is going on. > >Stephen > > >Springer, J., and a bunch of others (1999). Language dominance in >neurologically normal and epilepsy subjects: a functional MRI study. >Brain, 122, 2033-46. > >Pujol, J. et al (1999). Cerebral lateralization of language in normal >left-handed people studied by functional MRI. Neurology, 52, 1038-43. >______________________________________________________________ >Stephen L. Black, Ph.D. tel: (819) 822-9600 ext 2470 >Department of Psychology fax: (819) 822-9661 >Bishop's University e-mail: [EMAIL PROTECTED] >Lennoxville, QC J1M 1Z7 >Canada > >Dept web page at http://www.ubishops.ca/ccc/div/soc/psy >TIPS discussion list for psychology teachers at >http://www.frostburg.edu/dept/psyc/southerly/tips >_________________________________________________________ > > >--- >You are currently subscribed to tips as: [EMAIL PROTECTED] >To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
