Lateralization of the startle reflex circuit in humans: An examination with monaural probes following unilateral temporal lobe resection.

Startle reflex (SR) modulation elicited by monaural probes during affective picture viewing was investigated in patients following left temporal lobectomy (LTL; n = 8) and right temporal lobectomy (RTL; n = 10) and in controls (n = 18). All patients had undergone anteromedial temporal lobe (ATL) resection. LTL participants exhibited attenuated overall SR magnitude. Affective SR modulation in controls was significant for left ear probes, at both eyes, but not for right ear probes. RTL but not LTL participants displayed significant startle attenuation during pleasant picture viewing. Results suggest that monaural startle probes primarily activate structures in the ipsilateral ATL and that the ATLs are interconnected, with the left ATL more critical in perceiving arousing properties of affective stimuli, necessary for affective SR modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of Temporal Dynamics of Heart Rate and Blood Pressure Responses Elicited by Conditioned Fear but Not Acoustic Startle.

Fear-inducing stimuli were hypothesized to elicit fast heart rate (HR) responses but slow mean arterial blood pressure (MAP) responses and thus were studied in auditory fear conditioning and acoustic startle at high temporal resolution in freely moving mice and rats. Fear-induced instantaneous acceleration of HR reaching maximum physiological values and subsequent recovery to baseline were observed. The MAP response consisted of an immediate, mild, and transient increase followed by a sluggish, profound elevation and slow recovery. HR and MAP responses served as reliable indicators of conditioned fear in mice with dissociated temporal dynamics. Unconditioned auditory stimuli, including acoustic startle stimuli, elicited only fast, mild, and transient MAP and HR elevations in mice and rats, reflecting arousal and attention under these experimental conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical Basis in the Temporal Lobes for Processing Living Things.

Category-specific impairment in living things was examined in patients with temporal lobe damage to investigate whether specific neuroanatomical regions could be identified in processing the knowledge of specific categories. Tasks involving more effortful retrieval naming and less effortful attribute judgment were administered to 3 groups of patients with either bilateral, unilateral left, or unilateral right temporal lobe damage. Category-specific impairment in living things was observed for patients with unilateral or bilateral damage, results that are consistent with previous findings. Depending on its site and extent, the damage in the temporal lobe might lead to deficits in processing or loss of semantic knowledge for living things. Therefore, intact category-specific semantic processes may involve associations among different neural substrates in the temporal lobe. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional Response in Patients With Frontal Brain Damage: Effects of Affective Valence and Information Content.

The authors investigated the role of the frontal lobes in the emotional response in 19 patients with brain damage and 23 control subjects. They studied the modulation of the startle blink reflex by affective pictures, and other autonomic responses. Patients showed a dissociation between the startle reflex and the affective valence ratings of the pictures, as a result of a low inhibition of the startle reflex by pleasant pictures. Pictures elicited lower skin conductance responses (SCRs) in patients than in controls, whereas the groups did not differ in the SCRs prompted by less significant acoustic stimuli. The findings point to the frontal lobe as a structure involved in the emotional response and in the physiological emotional arousal related to the complexity of the stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdala Inactivation Blocks Expression of Conditioned Memory Modulation and the Promotion of Avoidance and Freezing.

Rats were exposed to shock-paired cues immediately after training on an appetitive preference task. Elevated levels of freezing in and active avoidance of the shock-paired compartment were observed, and memory for the appetitive task was improved when tested 24 hr later. Intra-amygdala muscimol injected before the posttraining exposure eliminated freezing, avoidance, and memory modulation. The blockade of both freezing and active avoidance, which involve competing behavioral tendencies, makes it unlikely that the amygdala itself generates either behavior. The elimination of conditioned memory modulation suggests that conditioned neurohormonal responses were blocked. These conditioned internal responses may comprise the intervening variable of "conditioned fear" and may promote observable behaviors, the form of which is determined by the environment in which they occur. (PsycINFO Database Record (c) 2010 APA, all rights reserved)