Limits...
Disruption of caudate working memory activation in chronic blast-related traumatic brain injury.

Newsome MR, Durgerian S, Mourany L, Scheibel RS, Lowe MJ, Beall EB, Koenig KA, Parsons M, Troyanskaya M, Reece C, Wilde E, Fischer BL, Jones SE, Agarwal R, Levin HS, Rao SM - Neuroimage Clin (2015)

Bottom Line: Blast TBI was also associated with worse performance on the Sternberg Item Recognition Task relative to the other groups, although no other group differences were found on neuropsychological measures of episodic memory, inhibition, and general processing speed.These results could not be attributed to caudate atrophy or the presence of PTSD symptoms.Our results point to a specific vulnerability of the caudate to blast injury.

View Article: PubMed Central - PubMed

Affiliation: Research Service Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX, USA ; Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, TX, USA.

ABSTRACT
Mild to moderate traumatic brain injury (TBI) due to blast exposure is frequently diagnosed in veterans returning from the wars in Iraq and Afghanistan. However, it is unclear whether neural damage resulting from blast TBI differs from that found in TBI due to blunt-force trauma (e.g., falls and motor vehicle crashes). Little is also known about the effects of blast TBI on neural networks, particularly over the long term. Because impairment in working memory has been linked to blunt-force TBI, the present functional magnetic resonance imaging (fMRI) study sought to investigate whether brain activation in response to a working memory task would discriminate blunt-force from blast TBI. Twenty-five veterans (mean age = 29.8 years, standard deviation = 6.01 years, 1 female) who incurred TBI due to blast an average of 4.2 years prior to enrollment and 25 civilians (mean age = 27.4 years, standard deviation = 6.68 years, 4 females) with TBI due to blunt-force trauma performed the Sternberg Item Recognition Task while undergoing fMRI. The task involved encoding 1, 3, or 5 items in working memory. A group of 25 veterans (mean age = 29.9 years, standard deviation = 5.53 years, 0 females) and a group of 25 civilians (mean age = 27.3 years, standard deviation = 5.81 years, 0 females) without history of TBI underwent identical imaging procedures and served as controls. Results indicated that the civilian TBI group and both control groups demonstrated a monotonic relationship between working memory set size and activation in the right caudate during encoding, whereas the blast TBI group did not (p < 0.05, corrected for multiple comparisons using False Discovery Rate). Blast TBI was also associated with worse performance on the Sternberg Item Recognition Task relative to the other groups, although no other group differences were found on neuropsychological measures of episodic memory, inhibition, and general processing speed. These results could not be attributed to caudate atrophy or the presence of PTSD symptoms. Our results point to a specific vulnerability of the caudate to blast injury. Changes in activation during the Sternberg Item Recognition Task, and potentially other tasks that recruit the caudate, may serve as biomarkers for blast TBI.

No MeSH data available.


Related in: MedlinePlus

Schematic of the encoding, maintenance, and response events in the Sternberg Item Recognition Task. ITI = inter-trial interval; SS = set size.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4477106&req=5

f0005: Schematic of the encoding, maintenance, and response events in the Sternberg Item Recognition Task. ITI = inter-trial interval; SS = set size.

Mentions: The Sternberg working memory task (Sternberg, 1966) consisted of a total of 72 trials distributed over three imaging runs. A schematic of the task is presented in Fig. 1. During the Encode phase, participants were asked to commit to memory 1, 3, or 5 consonants (set size, SS) over a 1800 ms interval. The number of encoded items constituted the working memory load, or set size, with 24 trials for each set size; trials were pseudo-randomized across set size. To maintain the same amount of visual information across the set sizes, asterisks were used to replace letters for set sizes 1 and 3 (see Fig. 1). Immediately following the Encode phase, participants viewed a centrally fixated “+” for 4300 ms (Maintenance phase). This was followed by the Response phase, in which a single probe letter appeared on the screen for 2800 ms. On 50% of trials, the probe letter matched one of the items presented during the Encode phase. Participants were instructed to respond with one of two fingers if the probe letter matched a letter in the Encode stimulus and with the other finger if the target did not match. The inter-trial interval consisted of a centrally fixated “+” that varied in duration from 3830 to 14,330 ms to introduce jitter into the time series for the analysis of this event-related fMRI task. The task was programmed using E-Prime software (Psychology Software Tools, Inc., Sharpsburg, PA) and displayed in the scanner using a back-projection video system (Cleveland: Avotec Inc., Stuart, FL; BCM: Sharp USA, Mahwah, NJ). To ensure that participants understood how to perform the task, individual training sessions were provided prior to the scan, and all subjects reached a criterion of 80% accuracy on SS1 during all runs.


Disruption of caudate working memory activation in chronic blast-related traumatic brain injury.

Newsome MR, Durgerian S, Mourany L, Scheibel RS, Lowe MJ, Beall EB, Koenig KA, Parsons M, Troyanskaya M, Reece C, Wilde E, Fischer BL, Jones SE, Agarwal R, Levin HS, Rao SM - Neuroimage Clin (2015)

Schematic of the encoding, maintenance, and response events in the Sternberg Item Recognition Task. ITI = inter-trial interval; SS = set size.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477106&req=5

f0005: Schematic of the encoding, maintenance, and response events in the Sternberg Item Recognition Task. ITI = inter-trial interval; SS = set size.
Mentions: The Sternberg working memory task (Sternberg, 1966) consisted of a total of 72 trials distributed over three imaging runs. A schematic of the task is presented in Fig. 1. During the Encode phase, participants were asked to commit to memory 1, 3, or 5 consonants (set size, SS) over a 1800 ms interval. The number of encoded items constituted the working memory load, or set size, with 24 trials for each set size; trials were pseudo-randomized across set size. To maintain the same amount of visual information across the set sizes, asterisks were used to replace letters for set sizes 1 and 3 (see Fig. 1). Immediately following the Encode phase, participants viewed a centrally fixated “+” for 4300 ms (Maintenance phase). This was followed by the Response phase, in which a single probe letter appeared on the screen for 2800 ms. On 50% of trials, the probe letter matched one of the items presented during the Encode phase. Participants were instructed to respond with one of two fingers if the probe letter matched a letter in the Encode stimulus and with the other finger if the target did not match. The inter-trial interval consisted of a centrally fixated “+” that varied in duration from 3830 to 14,330 ms to introduce jitter into the time series for the analysis of this event-related fMRI task. The task was programmed using E-Prime software (Psychology Software Tools, Inc., Sharpsburg, PA) and displayed in the scanner using a back-projection video system (Cleveland: Avotec Inc., Stuart, FL; BCM: Sharp USA, Mahwah, NJ). To ensure that participants understood how to perform the task, individual training sessions were provided prior to the scan, and all subjects reached a criterion of 80% accuracy on SS1 during all runs.

Bottom Line: Blast TBI was also associated with worse performance on the Sternberg Item Recognition Task relative to the other groups, although no other group differences were found on neuropsychological measures of episodic memory, inhibition, and general processing speed.These results could not be attributed to caudate atrophy or the presence of PTSD symptoms.Our results point to a specific vulnerability of the caudate to blast injury.

View Article: PubMed Central - PubMed

Affiliation: Research Service Line, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX, USA ; Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, TX, USA.

ABSTRACT
Mild to moderate traumatic brain injury (TBI) due to blast exposure is frequently diagnosed in veterans returning from the wars in Iraq and Afghanistan. However, it is unclear whether neural damage resulting from blast TBI differs from that found in TBI due to blunt-force trauma (e.g., falls and motor vehicle crashes). Little is also known about the effects of blast TBI on neural networks, particularly over the long term. Because impairment in working memory has been linked to blunt-force TBI, the present functional magnetic resonance imaging (fMRI) study sought to investigate whether brain activation in response to a working memory task would discriminate blunt-force from blast TBI. Twenty-five veterans (mean age = 29.8 years, standard deviation = 6.01 years, 1 female) who incurred TBI due to blast an average of 4.2 years prior to enrollment and 25 civilians (mean age = 27.4 years, standard deviation = 6.68 years, 4 females) with TBI due to blunt-force trauma performed the Sternberg Item Recognition Task while undergoing fMRI. The task involved encoding 1, 3, or 5 items in working memory. A group of 25 veterans (mean age = 29.9 years, standard deviation = 5.53 years, 0 females) and a group of 25 civilians (mean age = 27.3 years, standard deviation = 5.81 years, 0 females) without history of TBI underwent identical imaging procedures and served as controls. Results indicated that the civilian TBI group and both control groups demonstrated a monotonic relationship between working memory set size and activation in the right caudate during encoding, whereas the blast TBI group did not (p < 0.05, corrected for multiple comparisons using False Discovery Rate). Blast TBI was also associated with worse performance on the Sternberg Item Recognition Task relative to the other groups, although no other group differences were found on neuropsychological measures of episodic memory, inhibition, and general processing speed. These results could not be attributed to caudate atrophy or the presence of PTSD symptoms. Our results point to a specific vulnerability of the caudate to blast injury. Changes in activation during the Sternberg Item Recognition Task, and potentially other tasks that recruit the caudate, may serve as biomarkers for blast TBI.

No MeSH data available.


Related in: MedlinePlus