Collaboration between the hemispheres of a callosotomy patient: Emerging right hemisphere speech and the left hemisphere interpreter

The two hemispheres of the human brain can function simultaneously yet separately.

“Early work with patients who have undergone hemisphere disconnection in an effort to control epilepsy clearly' established that the two hemispheres of the human brain can function simultaneously yet separately (Gazzaniga and Sperry, 1966)”

• cites Gazzaniga and Sperry, 1966 sourceSupported

J.W. correctly identified 67% of the S&V objects in the flashed condition.

“He correctly identified 68% of the S&V objects in the sustained presentation condition and 67% in the flashed condition (see Table 1).”

Of right hand items, J.W. named 79% (19 out of 24) of pre-semantic items.

“Of those right hand items the subject named 79% (19 out of 24) of pre-semantic and 83% (20 out of 24) of post-semantic items.”

J.W. responded to 'different' S&V object trials with 50% accuracy (26 out of 52).

“However, while he responded to 'different' trials with only 50% accuracy (26 out of 52), he responded to 'same' trials with 67% accuracy (35 out of 52 correct, P < 0.02).”

For four of the remaining seven complex scene stimuli, J.W. gave incorrect descriptions that were visually similar or visually and semantically related to the actual picture.

“For four of the remaining seven stimuli, the subject gave incorrect descriptions that were visually similar or visually and semantically related to the actual picture.”

J.W. correctly identified 68% of the S&V objects in the sustained presentation condition.

“He correctly identified 68% of the S&V objects in the sustained presentation condition and 67% in the flashed condition (see Table 1).”

Of right hand items, J.W. named 83% (20 out of 24) of post-semantic items.

“Of those right hand items the subject named 79% (19 out of 24) of pre-semantic and 83% (20 out of 24) of post-semantic items.”

J.W. correctly named 67% of the neutral pictures shown to the LVF.

“He correctly named 67% of the neutral pictures and 47% of the familiar pictures shown to the LVF.”

J.W.'s performance levels did not differ significantly between stroboscopic and continuous presentation of S&V objects.

“The subject's performance levels did not differ significantly between stroboscopic and continuous presentation.”

The set of 10 familiar stimuli shown to the RVF as a control were correctly identified 100% of the time.

“The set of 10 familiar stimuli shown to the RVF as a control were correctly identified 100% of the time; this set included photos that were not correctly identified when presented in the LVF.”

Of left hand items, J.W. named 42% (10 out of 24) of pre-semantic items.

“Of those left hand items the subject named 42% (10 out of 24) of pre-semantic and 50% (12 out of 24) of post-semantic items.”

There was no scene that J.W. correctly identified and described entirely correctly.

“There was no scene that J.W. correctly identified and described entirely correctly.”

J.W.'s right hand correctly chose 100% (24 out of 24) of pre-semantic objects.

“The right hand correctly chose 100% (24 out of 24) of pre-semantic objects and 88% (21 out of 24) of post-semantic objects.”

J.W. identified and described 50% of the complex objects correctly.

“Patient J.W. identified and described 50% of the complex objects correctly.”

J.W. accurately named 81% of the neutral pictures presented to the RVF.

“Patient J.W. accurately named 81 % of the neutral pictures presented to the RVF.”

The complex scenes task was the most difficult naming task for J.W.

“This was the most difficult naming task for the subject.”

The set of 10 familiar stimuli shown to the RVF included photos that were not correctly identified when presented in the LVF.

“The set of 10 familiar stimuli shown to the RVF as a control were correctly identified 100% of the time; this set included photos that were not correctly identified when presented in the LVF.”

J.W.'s left hand correctly chose 96% (23 out of 24) of post-semantic objects.

“The left hand correctly chose 100% (24 out of 24) of pre-semantic objects and 96% (23 out of 24) of post-semantic objects.”

Of left hand items, J.W. named 50% (12 out of 24) of post-semantic items.

“Of those left hand items the subject named 42% (10 out of 24) of pre-semantic and 50% (12 out of 24) of post-semantic items.”

J.W.'s left hand correctly chose 100% (24 out of 24) of pre-semantic objects.

“The left hand correctly chose 100% (24 out of 24) of pre-semantic objects and 96% (23 out of 24) of post-semantic objects.”

Now, 1 year later, J.W. can name about 60% of LVF stimuli.

“Now, 1 year later, we find that he can name about 60% of such stimuli.”

J.W.'s right hand correctly chose 88% (21 out of 24) of post-semantic objects.

“The right hand correctly chose 100% (24 out of 24) of pre-semantic objects and 88% (21 out of 24) of post-semantic objects.”

J.W. correctly named 47% of the familiar pictures shown to the LVF.

“He correctly named 67% of the neutral pictures and 47% of the familiar pictures shown to the LVF.”

J.W.'s performance on unfamiliar face 'same' trials was 68% (19 out of 28 correct, P > 0.08).

“Taken individually, neither 'same' nor 'different' trial performance was above chance: 'same:' 68% (19 out of 28 correct, P > 0.08), 'different:' 46% (13 out of 28 correct, P > 0.85).”

J.W. correctly judged whether line-drawing stimuli presented sequentially were the same or different with 75% accuracy in the RVF (15 out of 20 correct, P < 0.04).

“The subject correctly judged whether stimuli presented sequentially were the same or different with 75% accuracy in the RVF (15 out of 20 correct, P < 0.04), and with 85% accuracy in the LVF (17 out of 20 correct, P < 0.003).”

J.W.'s continuing development emerged some 12 years after split brain surgery.

“This continuing development which has emerged some 12 years after split brain surgery suggests the brain is capable of remarkable late stage plasticity.”

J.W.'s performance on line-drawing 'same' trials was 55% (11 out of 20).

“His performance on 'same' trials was 55% (11 out of 20), and his performance on 'different' trials was 60% (12 out of 20).”

J.W. responded to 'same' S&V object trials with 67% accuracy (35 out of 52 correct, P < 0.02).

“However, while he responded to 'different' trials with only 50% accuracy (26 out of 52), he responded to 'same' trials with 67% accuracy (35 out of 52 correct, P < 0.02).”

Significant and near significant matching performance was seen for same-stimulus trials as opposed to the different trials in the S&V object and unfamiliar face matching tasks.

“Significant and near significant matching performance was seen for same-stimulus trials as opposed to the different trials in the S&V object and unfamiliar face matching tasks.”

Overall J.W. was unable to judge significantly better than chance whether the unfamiliar faces were the same or different (32 out of 56 correct, P > 0.30).

“Overall J.W. was unable to judge significantly better than chance whether the unfamiliar faces were the same or different (32 out of 56 correct, P > 0.30).”

The complex objects were named at 50% (12 out of 24).

“The S&V objects were named with an accuracy of 66% (38 out of 58) and the complex objects at 50% (12 out of 24).”

Performance on family pictures was only 47% correct.

“Performance on family pictures was only 47% correct.”

J.W. was unable to judge any better than chance whether line-drawing stimuli were the same or different (24 out of 40 correct, P > 0.25).

“Patient J.W. was unable to judge any better than chance whether stimuli were the same or different (24 out of 40 correct, P > 0.25).”

J.W. correctly judged whether line-drawing stimuli presented sequentially were the same or different with 85% accuracy in the LVF (17 out of 20 correct, P < 0.003).

“The subject correctly judged whether stimuli presented sequentially were the same or different with 75% accuracy in the RVF (15 out of 20 correct, P < 0.04), and with 85% accuracy in the LVF (17 out of 20 correct, P < 0.003).”

When given stimuli substantially more complex (the complex scenes task) than the single objects presented, J.W.'s performance plummeted.

“When given stimuli that were substantially more complex (the complex scenes task) than the single objects presented, J.W.'s performance plummeted.”

The worst naming performance in the LVF was for familiar photographs with an accuracy of 47% (8 out of 17).

“In contrast, the worst naming performance in the LVF was for familiar photographs with an accuracy of 47% (8 out of 17).”

The S&V objects were named with an accuracy of 66% (38 out of 58).

“The S&V objects were named with an accuracy of 66% (38 out of 58) and the complex objects at 50% (12 out of 24).”

J.W.'s right hemisphere speech ability appears to be increasing several years later than the dynamic periods of previously reported cases.

“This ability appears to be increasing several years later than the dynamic periods of previously reported cases.”

Some callosotomy patients have shown ability to produce speech from their previously silent right hemispheres 26-36 months postoperatively.

“For example, some callosotomy patients have shown evidence of an ability to produce speech out of their previously silent right hemispheres 26-36 months © Oxford University Press 1996 postoperatively (Gazzaniga et ai, 1979)”

• cites Gazzaniga et al., 1979 sourceNot checked — no full text of the source

The left hemisphere possesses the capacity to 'interpret' the actions produced by both hemispheres.

“In general terms, the left hemisphere appears to be dominant in terms of language and speech functions and to possess the capacity to 'interpret' the actions produced by both hemispheres.”

• cites Gazzaniga et al., 1985 sourceNot checked — no full text of the source
• cites Gazzaniga, 1995 sourceNot checked — no full text of the source
• cites Phelps and Gazzaniga, 1992 sourceNot checked — no full text of the source

At the time of his callosotomy, J.W. had a language dominant left hemisphere.

“At the time of his callosotomy, J.W. had a language dominant left hemisphere; his right hemisphere could understand both spoken and written language, but he was unable to speak.”

• cites Sidtis et al., 1981a, bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Each hemisphere is specialized for particular functions.

“and moreover, that each hemisphere is specialized for particular functions (Sperry et ai, 1969;Gazzaniga, 1970).”

• cites Sperry et al., 1969Not checked — no full text of the source
• cites Gazzaniga, 1970Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Some callosotomy patients have shown increasing ability to verbalize LVF materials between 12 and 30 months postoperatively.

“and an increasing ability to verbalize LVF materials between 12 and 30 months postoperatively (Gazzaniga et ai, 1984).”

• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source

J.W.'s extended verbal responses to LVF stimuli seem to result from a collaboration between the hemispheres.

“However, the subject's extended verbal responses to LVF stimuli seem to result from a collaboration between the hemispheres and to involve the left hemisphere interpreter.”

J.W.'s late-developing speech ability appears to be the consequence of long-term neural plasticity.

“This latedeveloping speech ability appears to be the consequence of long-term neural plasticity.”

MRI has confirmed the completeness of callosal section in J.W.

“and MRI has confirmed the completeness of callosal section (Gazzaniga et al., 1984).”

• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source

J.W.'s right hemisphere, though previously silent, has gained the ability to speak.

“The right hemisphere of patient J.W., though previously silent (Sidtis et ai, 1981a), has gained the ability to speak (Baynes et ai, 1995).”

• cites Sidtis et al., 1981aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Baynes et al., 1995Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

J.W.'s right hemisphere is often capable of naming people and neutral objects when presented with appropriate stimuli.

“Thus, J.W.'s right hemisphere is often capable of naming people and neutral”

J.W.'s extended verbal responses to LVF stimuli involve the left hemisphere interpreter.

“However, the subject's extended verbal responses to LVF stimuli seem to result from a collaboration between the hemispheres and to involve the left hemisphere interpreter.”

The results of the S&V object comparison task suggest some sort of interhemispheric interaction.

“With respect to subcortical transfer, the results of the S&V object comparison task suggest some sort of interhemispheric interaction.”

Our earlier study, using many of the same stimuli reported here, revealed a smaller capacity to name left field stimuli.

“Our earlier study, using many of the same stimuli reported here (Baynes et al., 1995) revealed a smaller capacity to name left field stimuli.”

• cites Baynes et al., 1995Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Speech generated by the right hemisphere can provide the left with additional clues which the interpreter utilizes.

“Speech generated by the right hemisphere can provide the left with additional clues which the interpreter utilizes.”

Taken together, the evidence for a right-hemisphere speech capacity is compelling.

“Taken together, we believe the evidence for a right-hemisphere speech capacity is compelling.”

The first factor (improper lateralization) can be eliminated because with one exception all visual stimuli were presented at a minimum of 2° laterally using an image stabilizer.

“The first factor can be eliminated because with one exception all visual stimuli were presented at a minimum of 2° laterally using an image stabilizer.”

In all previous studies, as well as this study, there is little evidence for transfer of basic sensory information.

“In short, in all previous studies, as well as this study, there is little evidence for transfer of basic sensory information”

Several years ago, prior to displaying any capacity for right hemisphere speech, J.W.'s right hemisphere did not elicit an N400 event-related potential to semantically incongruent stimuli.

“Several years ago, prior to displaying any capacity for right hemisphere speech, J.W.'s right hemisphere did not elicit an N400 event-related potential to semantically incongruent stimuli (Kutas et al., 1988).”

• cites Kutas et al., 1988 sourceNot checked — no full text of the source

In previous cases, the development of right hemisphere speech capability occurred much earlier in the postoperative course.

“In previous cases, however, the development of right hemisphere speech capability occurred much earlier in the postoperative course.”

• cites Gazzaniga et al., 1979 sourceNot checked — no full text of the source
• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source

Producing a multi-word description may still exceed J.W.'s right hemisphere language capacities as has been shown in other patients.

“Producing a multi-word description may still exceed J.W.'s right hemisphere language capacities as has been shown in other patients (Gazzaniga, 1979).”

• cites Gazzaniga, 1979Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

There is substantial data to support the existence of a left hemisphere interpreter.

“There is substantial data to support the existence of a left hemisphere interpreter (Gazzaniga et al., 1985;Gazzaniga, 1995;Phelps and Gazzaniga, 1992;Metcalfe et al., 1995).”

• cites Gazzaniga et al., 1985 sourceNot checked — no full text of the source
• cites Gazzaniga, 1995 sourceNot checked — no full text of the source
• cites Phelps and Gazzaniga, 1992 sourceNot checked — no full text of the source

The view that verbal responses to LVF stimuli result from hemispheric collaboration is consistent with earlier observations that the left hemisphere interprets behaviour elicited from the right hemisphere according to the left brain's sphere of knowledge.

“The view that verbal responses to LVF stimuli result from hemispheric collaboration is consistent with earlier observations that the left hemisphere interprets behaviour elicited from the right hemisphere according to the left brain's sphere of knowledge.”

The brain is capable of remarkable late stage plasticity.

“This continuing development which has emerged some 12 years after split brain surgery suggests the brain is capable of remarkable late stage plasticity.”

J.W.'s naming performance became worse as the visual stimuli became more complex.

“It appears that J.W.'s naming performance became worse as the visual stimuli became more complex.”

Explicit collaboration between the hemispheres in patient J.W. was produced experimentally by Mac Kay and Mac Kay (1979) in a paradigm that did not invoke the interpreter mechanism.

“Explicit collaboration between the hemispheres in patient J.W. was produced experimentally by Mac Kay and Mac Kay (1979) in a paradigm that did not invoke the interpreter mechanism.”

• cites Mac Kay and Mac Kay, 1979Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

It seems unlikely that a hemisphere incapable of using syntax to comprehend sentences and phrases would emit elaborate vocalizations.

“However, it seems unlikely that a hemisphere incapable of using syntax to comprehend sentences and phrases (Gazzaniga, et al., 1984, Baynes andGazzaniga, 1988) would emit elaborate vocalizations.”

• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source
• cites Baynes and Gazzaniga, 1988Not checked — no full text of the source

J.W.'s responses to LVF stimuli are often the result of a collaboration between his hemispheres.

“This implies that J.W.'s responses to LVF stimuli are often the result of a collaboration between his hemispheres (Gazzaniga et al., 1984).”

• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source

Some of what appears to be interhemispheric transfer may be the result of the left hemisphere using effective response strategies when guessing.

“Some of what appears to be interhemispheric transfer may be the result of the left hemisphere using effective response strategies when guessing (Seymour et al., 1994).”

• cites Seymour et al., 1994 sourceNot checked — no full text of the source

The presence of the event-related potential N400 wave has been correlated with the capacity for speech in other callosotomy patients.

“It should be noted, in this regard, that the presence of the event-related potential N400 wave has been correlated with the capacity for speech in other callosotomy patients (Kutas et al., 1988).”

• cites Kutas et al., 1988 sourceNot checked — no full text of the source

J.W.'s present capacity to name left field stimuli is comparable with the naming capacities of certain other patients who have undergone callosal section.

“Overall, J.W.'s present capacity to name left field stimuli is comparable with the naming capacities of certain other patients who have undergone callosal section (Gazzaniga et al., 1979(Gazzaniga et al., , 1984)).”

• cites Gazzaniga et al., 1979 sourceNot checked — no full text of the source
• cites Gazzaniga et al., 1984 sourceNot checked — no full text of the source

A recent re-examination has shown that J.W. does now generate N400 responses to such stimuli.

“A recent re-examination has shown that J.W. does now generate N400 responses to such stimuli (G.R. Mangun, M. Proverbeo and M. S. Gazzaniga, personal communication).”

• cites G.R. Mangun, M. Proverbeo and M. S. Gazzaniga, personal communicationNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.