Biomedical subjects

Michael L Macklin

Publications and source records attributed to Michael L Macklin.

6 recordsLinked to original sources

PubMed2005

Probing reward function in post-traumatic stress disorder with beautiful facial images.

Reward dysfunction may be implicated in post-traumatic stress disorder (PTSD). This study applied a behavioral probe, known to activate brain reward regions, to subjects with PTSD. Male heterosexual Vietnam veterans with (n = 12) or without (n = 11) current PTSD were administered two tasks: (a) key pressing to change the viewing time of average or beautiful female or male facial images, and (b) rating the attractiveness of these images. There were no significant group differences in the attractiveness ratings. However, PTSD patients expended less effort to extend the viewing time of the beautiful female faces. These findings suggest a reward deficit in PTSD.

Beauty↗

PubMed2005

A functional magnetic resonance imaging study of amygdala and medial prefrontal cortex responses to overtly presented fearful faces in posttraumatic stress disorder.

BACKGROUND: Previous functional neuroimaging studies have demonstrated exaggerated amygdala responses and diminished medial prefrontal cortex responses during the symptomatic state in posttraumatic stress disorder (PTSD). OBJECTIVES: To determine whether these abnormalities also occur in response to overtly presented affective stimuli unrelated to trauma; to examine the functional relationship between the amygdala and medial prefrontal cortex and their relationship to PTSD symptom severity in response to these stimuli; and to determine whether responsivity of these regions habituates normally across repeated stimulus presentations in PTSD. DESIGN: Case-control study. SETTING: Academic medical center. PARTICIPANTS: Volunteer sample of 13 men with PTSD (PTSD group) and 13 trauma-exposed men without PTSD (control group). MAIN OUTCOME MEASURES: We used functional magnetic resonance imaging (fMRI) to study blood oxygenation level-dependent signal during the presentation of emotional facial expressions. RESULTS: The PTSD group exhibited exaggerated amygdala responses and diminished medial prefrontal cortex responses to fearful vs happy facial expressions. In addition, in the PTSD group, blood oxygenation level-dependent signal changes in the amygdala were negatively correlated with signal changes in the medial prefrontal cortex, and symptom severity was negatively related to blood oxygenation level-dependent signal changes in the medial prefrontal cortex. Finally, relative to the control group, the PTSD group tended to exhibit diminished habituation of fearful vs happy responses in the right amygdala across functional runs, although this effect did not exceed our a priori statistical threshold. CONCLUSIONS: These results provide evidence for exaggerated amygdala responsivity, diminished medial prefrontal cortex responsivity, and a reciprocal relationship between these 2 regions during passive viewing of overtly presented affective stimuli unrelated to trauma in PTSD.

Amygdala↗

PubMed2004

Regional cerebral blood flow in the amygdala and medial prefrontal cortex during traumatic imagery in male and female Vietnam veterans with PTSD.

CONTEXT: Theoretical neuroanatomic models of posttraumatic stress disorder (PTSD) and the results of previous neuroimaging studies of PTSD highlight the potential importance of the amygdala and medial prefrontal regions in this disorder. However, the functional relationship between these brain regions in PTSD has not been directly examined. OBJECTIVE: To examine the relationship between the amygdala and medial prefrontal regions during symptom provocation in male combat veterans (MCVs) and female nurse veterans (FNVs) with PTSD. DESIGN: Case-control study. SETTING: Academic medical center. PARTICIPANTS: Volunteer sample of 17 (7 men and 10 women) Vietnam veterans with PTSD (PTSD group) and 19 (9 men and 10 women) Vietnam veterans without PTSD (control group). MAIN OUTCOME MEASURES: We used positron emission tomography and the script-driven imagery paradigm to study regional cerebral blood flow (rCBF) during the recollection of personal traumatic and neutral events. Psychophysiologic and emotional self-report data also were obtained to confirm the intended effects of script-driven imagery. RESULTS: The PTSD group exhibited rCBF decreases in medial frontal gyrus in the traumatic vs neutral comparison. When this comparison was conducted separately by subgroup, MCVs and FNVs with PTSD exhibited these medial frontal gyrus decreases. Only MCVs exhibited rCBF increases in the left amygdala. However, for both subgroups with PTSD, rCBF changes in medial frontal gyrus were inversely correlated with rCBF changes in the left amygdala and the right amygdala/periamygdaloid cortex. Furthermore, in the traumatic condition, for both subgroups with PTSD, symptom severity was positively related to rCBF in the right amygdala and negatively related to rCBF in medial frontal gyrus. CONCLUSIONS: These results suggest a reciprocal relationship between medial prefrontal cortex and amygdala function in PTSD and opposing associations between activity in these regions and symptom severity consistent with current functional neuroanatomic models of this disorder.

Amygdala↗

PubMed2004

Hippocampal function in posttraumatic stress disorder.

Recent studies have reported memory deficits and reduced hippocampal volumes in posttraumatic stress disorder (PTSD). The goal of the current research was to use functional neuroimaging and a validated explicit memory paradigm to examine hippocampal function in PTSD. We used positron emission tomography (PET) and a word-stem completion task to study regional cerebral blood flow (rCBF) in the hippocampus in 16 firefighters: 8 with PTSD (PTSD group) and 8 without PTSD (Control group). During PET scanning, participants viewed three-letter word stems on a computer screen and completed each stem with a word they had previously encoded either deeply (High Recall condition) or shallowly (Low Recall condition). Relative to the Control group, the PTSD group exhibited significantly smaller rCBF increases in the left hippocampus in the High vs Low Recall comparison. However, this finding reflected relatively elevated rCBF in the Low Recall condition in the PTSD group. Collapsing across High and Low Recall conditions, (1) the PTSD group had higher rCBF in bilateral hippocampus and left amygdala than the Control group, and (2) within the PTSD group, symptom severity was positively associated with rCBF in hippocampus and parahippocampal gyrus. The groups did not significantly differ with regard to accuracy scores on the word-stem completion task. The PTSD group had significantly smaller right (and a trend for smaller left) hippocampal volumes than the Control group. The results suggest an abnormal rCBF response in the hippocampus during explicit recollection of nonemotional material in firefighters with PTSD, and that this abnormal response appears to be driven by relatively elevated hippocampal rCBF in the comparison condition.

Adult↗

PubMed2004

Psychophysiological responding during script-driven imagery in people reporting abduction by space aliens.

Is recollection of highly improbable traumatic experiences accompanied by psychophysiological responses indicative of intense emotion? To investigate this issue, we measured heart rate, skin conductance, and left lateral frontalis electromyographic responses in individuals who reported having been abducted by space aliens. Recordings of these participants were made during script-driven imagery of their reported alien encounters and of other stressful, positive, and neutral experiences they reported. We also measured the psychophysiological responses of control participants while they heard the scripts of the abductees. We predicted that if "memories" of alien abduction function like highly stressful memories, then psychophysiological reactivity to the abduction and stressful scripts would be greater than reactivity to the positive and neutral scripts, and this effect would be more pronounced among abductees than among control participants. Contrast analyses confirmed this prediction for all three physiological measures (ps < .05). Therefore, belief that one has been traumatized may generate emotional responses similar to those provoked by recollection of trauma (e.g., combat).

Adult↗

PubMed2003

Physiologic responses to sudden, loud tones in monozygotic twins discordant for combat exposure: association with posttraumatic stress disorder.

BACKGROUND: Larger heart rate responses to sudden, loud (startling) tones represent one of the best-replicated psychophysiologic markers for posttraumatic stress disorder (PTSD). This abnormality may be a pretrauma vulnerability factor, ie, it may have been present prior to the event's occurrence and increased the individual's likelihood of developing PTSD on traumatic exposure. Alternately, it may be an acquired PTSD sign, ie, it may have developed after the traumatic exposure, along with the PTSD. Studying identical twins discordant for traumatic exposure offers an opportunity to resolve these competing origins. METHODS: Subjects included pairs of Vietnam combat veterans and their non-combat-exposed, monozygotic twins. Combat veterans were diagnosed as having current PTSD (n = 50) or non-PTSD (ie, never had) (n = 53). All subjects listened to a series of 15 sudden, loud tone presentations while heart rate, skin conductance, and orbicularis oculi electromyogram responses were measured. RESULTS: Consistent with previous reports, averaged heart rate responses to the tones were larger in Vietnam combat veterans with PTSD. These larger responses were not shared by their non-combat-exposed co-twins, whose responses were similar to those of the non-PTSD combat veterans and their non-combat-exposed co-twins. This result remained significant after adjusting for a number of potentially confounding factors. CONCLUSIONS: The results suggest that larger heart rate responses to sudden, loud tones represent an acquired sign of PTSD rather than a familial vulnerability factor.

Acoustic Stimulation↗