Interactions between the prefrontal cortex and amygdala during delay discounting and reversal.

Interactions between the prefrontal cortex and amygdala are thought to be critical for reward anticipation. Alterations in reward anticipation that lead to an inability to wait for rewards or a diminished capacity to change behavior when doing so would be optimal are often termed impulsivity and compulsivity, respectively. Distinct regions of the prefrontal cortex may support decreased impulsivity through self-control and decreased compulsivity through flexibility. However, both self-control and flexibility appear to involve the amygdala. Using a delay discounting paradigm, the current investigation found that inactivation and disconnection of the medial prefrontal cortex and basolateral amygdala led rats to become more impulsive by affecting preference for smaller immediate over larger delayed rewards. Conversely, inactivation and disconnection of the orbitofrontal cortex and amygdala led rats to become more compulsive as demonstrated by an inability to flexibly reverse stimulus–reward relationships in an odor reversal task. The current findings support a double dissociation between orbitofrontal cortex–amygdala interactions for odor reversal and medial prefrontal cortex–amygdala interactions for delay discounting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain potentials implicate temporal lobe abnormalities in criminal psychopaths.

Psychopathy is associated with abnormalities in attention and orienting. However, few studies have examined the neural systems underlying these processes. To address this issue, the authors recorded event-related potentials (ERPs) while 80 incarcerated men, classified as psychopathic or nonpsychopathic via the Hare Psychopathy Checklist-Revised (R. D. Hare, 1991, 2003), completed an auditory oddball task. Consistent with hypotheses, processing of targets elicited larger frontocentral negativities (N550) in psychopaths than in nonpsychopaths. Psychopaths also showed an enlarged N2 and reduced P3 during target detection. Similar ERP modulations have been reported in patients with amygdala and temporal lobe damage. The data are interpreted as supporting the hypothesis that psychopathy may be related to dysfunction of the paralimbic system--a system that includes parts of the temporal and frontal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of attention in learning and action: Effects of lesions of the amygdala central nucleus, medial prefrontal cortex, and posterior parietal cortex.

Many associative learning theories assert that the predictive accuracy of events affects the allocation of attention to them. More reliable predictors of future events are usually more likely to control action based on past learning, but less reliable predictors are often more likely to capture attention when new information is acquired. Previous studies showed that a circuit including the amygdala central nucleus (CEA) and the cholinergic substantia innominata/nucleus basalis magnocellularis (SI/nBM) is important for both sustained attention guiding action in a five-choice serial reaction time (5CSRT) task and for enhanced new learning about less predictive cues in a serial conditioning task. In this study, the authors found that lesions of the cholinergic afferents of the medial prefrontal cortex interfered with 5CSRT performance but not with surprise-induced enhancement of learning, whereas lesions of cholinergic afferents of posterior parietal cortex impaired the latter effects but did not affect 5CSRT performance. CEA lesions impaired performance in both tasks. These results are consistent with the view that CEA affects these distinct aspects of attention by influencing the activity of separate, specialized cortical regions via modulation of SI/nBM. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instrumental learning and relearning in individuals with psychopathy and in patients with lesions involving the amygdala or orbitofrontal cortex.

Previous work has shown that individuals with psychopathy are impaired on some forms of associative learning, particularly stimulus-reinforcement learning (Blair et al., 2004; Newman & Kosson, 1986). Animal work suggests that the acquisition of stimulus-reinforcement associations requires the amygdala (Baxter & Murray, 2002). Individuals with psychopathy also show impoverished reversal learning (Mitchell, Colledge, Leonard, & Blair, 2002). Reversal learning is supported by the ventrolateral and orbitofrontal cortex (Rolls, 2004). In this paper we present experiments investigating stimulus-reinforcement learning and relearning in patients with lesions of the orbitofrontal cortex or amygdala, and individuals with developmental psychopathy without known trauma. The results are interpreted with reference to current neurocognitive models of stimulus-reinforcement learning, relearning, and developmental psychopathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fos expression in the prefrontal cortex and nucleus accumbens following exposure to retrospective timing tasks.

The dorsal striatum and prefrontal cortex have been implicated in interval timing. We examined whether performance of temporal discrimination tasks is associated with increased neuronal activation in these areas, as revealed by Fos expression, a marker for neuronal activation. In Experiment 1, rats were trained on a discrete-trials temporal discrimination task in which a light (22 cd/m2) was presented for a variable time, t (2.5–47.5 s), after which levers A and B were presented. A response on lever A was reinforced if t t > 25 s. A second group was trained on a light-intensity discrimination procedure, in which a light of variable intensity, i (3.6–128.5 cd/m2) was presented for 25 s. A response on lever A was reinforced if i i > 22 cd/m2. In Experiment 2, bisection procedures were used to assess temporal (200–800 ms, 22 cd/m2) and light-intensity (3.6–128.5 cd/m2, 400 ms) discrimination. The increase in proportional choice of lever B as a function of stimulus duration or intensity conformed to a two-parameter logistic equation. Fos expression in the prefrontal cortex and nucleus accumbens was higher in rats performing temporal discrimination tasks than in those performing light-intensity discrimination tasks, indicating greater neuronal activation in these areas during temporal discrimination tasks. Fos expression in the dorsal striatum did not differ between rats performing temporal and light-intensity discrimination tasks. These results suggest that the prefrontal cortex and nucleus accumbens are involved in temporal discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Medial prefrontal cortex lesions in the female rat affect sexual and maternal behavior and their sequential organization.

Temporal sequences of sexual and maternal behaviors in female rats and their correlation with each other and with performance on a sensory-motor gating response inhibition task assessed by prepulse inhibition (PPI) were investigated following medial prefrontal cortex (mPFC) lesions. Following excitotoxic mPFC (n = 10) or sham (n = 9) lesions, sexual behaviors across the ovarian cycle were scored. After mating and parturition, maternal interactions were scored until pups reached postnatal Day 10. After resumption of the ovarian cycle, the female rats were tested for PPI. Compared with sham lesions, mPFC lesions impaired proceptive behaviors and some maternal behaviors (e.g., pup retrieval, pup licking) but did not affect others (e.g., nest building, pup mouthing). Lesions disrupted temporal sequences of solicitations (number of male orientations followed, within 4 s, by a level change) and pup retrievals (number of pup retrievals followed, within 5 s, by another retrieval). These sequential behavior patterns were significantly correlated with each other and with PPI. However, when PPI effects were partialled out, group differences were less strong, but persisted. This study demonstrated that mPFC manipulations affect actions rich in sequential structure in response to biologically relevant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of the rat medial prefrontal cortex in novelty detection.

The prefrontal cortex in humans has been implicated in processes that underlie novelty detection and attention. This study examined the contribution of the rat medial prefrontal cortex to novelty detection using the targeting, or orienting, response (OR) as a behavioral index. Lesions to the medial prefrontal cortex (specifically the prelimbic and infralimbic cortices) influenced neither the OR to a novel visual stimulus from a localized light source (V1), nor the change in this OR over the course of a series of exposures to V1. However, after exposure to V1, the OR to a 2nd visual stimulus from the same source, V2, was more pronounced in control rats than in lesioned rats. These results suggest that the medial prefrontal cortex in the rat contributes to the process of novelty detection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of directed forgetting in the avian prefrontal cortex.

The authors trained 2 homing pigeons (Columba livia) on a directed forgetting task with 3 cues: a remember cue that was followed by a memory test and the opportunity to obtain a reward, a forget cue that was not followed by a memory test or a reward, and a free-reward cue that was not followed by a memory test but was followed by a free reward. The authors examined the activity of single neurons in the avian nidopallium caudolaterale, an area equivalent to the primate prefrontal cortex. Following the remember cue there was sustained neural activity during the delay period, whereas following the forget cue the neural activity in the delay period was significantly reduced. The activity following the free-reward cue mirrored that following the remember cue. The authors discuss the extent to which the findings are in line with the view that the sustained activity reflects memory for the sample stimulus or memory for reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Without conscience: The disturbing world of the psychopaths among us.

Reviews the book, Without conscience: The disturbing world of the psychopaths among us by Robert D. Hare (see record 2001-00418-000). Too often we hear about adults, and now more than ever, adolescents, who perpetrate violence so horrific and seemingly meaningless that their actions defy the understanding of professionals, let alone of the perpetrators' families. The republication of Robert Hare's popular work on the psychopathic personality is a testament to the success and importance of this book. Hare paints an intriguing yet scary portrait of this, the most dangerous type of personality disorder. His colourful, but accurate portrayal of the psychopath makes this book equally important alike for parents and clinicians. Without conscience is based on more than 30 years of the author's research on psychopathy. The book is written in a sincere and easily readable fashion for a general audience. The research and clinical literature is described in nontechnical terms with a minimum of jargon, making the work accessible to a wide audience. Much of Hare's research has been devoted to the reliable identification of psychopaths. His development of the Psychopathy Checklist (PCL) may represent the single, most important advancement to date toward what hopefully will become our ultimate understanding of psychopathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction of ventral and orbital prefrontal cortex with inferotemporal cortex in conditional visuomotor learning.

Five rhesus monkeys (Macaca mulatta) were trained to learn novel conditional visuomotor associations, to perform this task with familiar stimuli, and to perform a visual matching-to-sample task with the same familiar stimuli. Removal of the orbital and ventral prefrontal cortex (PFv+o) in 1 hemisphere and inferotemporal cortex (IT) in the other, thus completing a surgical disconnection of these 2 regions, yielded an impairment on all 3 tasks. Addition of a premotor cortex lesion to the hemisphere containing the PFv+o lesion did not worsen the impairments. The results indicate that PFv+o interacts with IT in both the learning and retention of conditional visuomotor associations. In addition to those associations, which might be considered lower order rules for choosing a response, frontotemporal interaction also appears to be important for higher order rules, such as those involved in the matching task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aberrant neural processing of moral violations in criminal psychopaths.

A defining characteristic of psychopathy is the willingness to intentionally commit moral transgressions against others without guilt or remorse. Despite this “moral insensitivity,” the behavioral and neural correlates of moral decision-making in psychopathy have not been well studied. To address this issue, the authors used functional magnetic resonance imaging (fMRI) to record hemodynamic activity in 72 incarcerated male adults, stratified into psychopathic (n = 16) and nonpsychopathic (n = 16) groups based on scores from the Hare Psychopathy Checklist—Revised (R. D. Hare, 2003), while they made decisions regarding the severity of moral violations of pictures that did or did not depict moral situations. Consistent with hypotheses, an analysis of brain activity during the evaluation of pictures depicting moral violations in psychopaths versus nonpsychopaths showed atypical activity in several regions involved in moral decision-making. This included reduced moral/nonmoral picture distinctions in the ventromedial prefrontal cortex and anterior temporal cortex in psychopaths relative to nonpsychopaths. In a separate analysis, the association between severity of moral violation ratings and brain activity across participants was compared in psychopaths versus nonpsychopaths. Results revealed a positive association between amygdala activity and severity ratings that was greater in nonpsychopaths than psychopaths, and a negative association between posterior temporal activity and severity ratings that was greater in psychopaths than nonpsychopaths. These results reveal potential neural underpinnings of moral insensitivity in psychopathy and are discussed with reference to neurobiological models of morality and psychopathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of prefrontal cortex in predictive fear learning.

Pavlovian fear conditioning depends on prediction error, or the discrepancy between actual and expected outcomes. We used immunohistochemistry, neuronal tract tracing, and reversible inactivation to study the role of prefrontal cortex and thalamocortical pathways in predictive fear learning. Unexpected, but not expected, conditioned stimulus (CS)–unconditioned stimulus (US) presentations caused increased c-Fos expression in the prefrontal cortex (PFC), midline thalamus, lateral amygdala, as well as retrograde labeled midline thalamic afferents to PFC. Reversible inactivation of dorsomedial PFC, but not infralimbic PFC, prevented the associative blocking of fear learning. These results suggest a role for dorsomedial PFC (dmPFC), and a thalamic → dmPFC pathway, in signaling whether or not aversive events are expected or unexpected and so whether they are to be learned about. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional modularity of the medial prefrontal cortex: Involvement in human empathy.

To investigate medial frontal lobe mediation of human empathy, the authors analyzed the activation areas in statistical parametric maps of 80 studies reporting neural correlates of empathic processing. The meta-analysis revealed 6 spatially distinct activation clusters in the medial part of the frontal lobe dorsal to the intercommissural plane. The most dorsal cluster coincided with the left supplementary motor area (SMA). Rostrally adjacent was a cluster that overlapped with the right pre-SMA. In addition, there were 3 left-hemispheric and 1 right-hemispheric clusters located at the border between the superior frontal and anterior cingulate gyrus. A broad spectrum of cognitive functions were associated with these clusters, including attention to one's own action, which was related to activations in the SMA, and valuation of other people's behavior and ethical categories, which was related to activations in the most rostroventral cluster. These data complement the consistent observation that lesions of the medial prefrontal cortex interfere with a patient's perception of own bodily state, emotional judgments, and spontaneous behavior. The results of the current meta-analysis suggest the medial prefrontal cortex mediates human empathy by virtue of a number of distinctive processing nodes. In this way, the authors' findings suggest differentiated aspects of self-control of behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the medial prefrontal cortex in acquired distinctiveness and equivalence of cues.

In the present study, the authors examined the role of the medial prefrontal cortex in acquired equivalence and distinctiveness of cues. Rats were placed in 4 experimental contexts (A, B, C, and D) where they received presentations of 2 auditory stimuli (X and Y). In Contexts A and B, X was paired with food and Y was not, whereas in Contexts C and D, Y was paired with food and X was not. Rats that received sham lesions and those with lesions of the medial prefrontal cortex acquired this configural discrimination equally readily. Rats then received many pellets in A but not in C. After this training, sham-lesion rats exhibited more magazine activity in B than in D (an acquired distinctiveness/acquired equivalence effect), whereas those with medial prefrontal cortex lesions did not. These results indicate that the medial prefrontal cortex is involved in the process by which experience with stimuli influences the degree of generalization between them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial prefrontal cortex and Pavlovian conditioning: Trace versus delay conditioning.

Pavlovian eyeblink (EB) conditioning was studied in both trace and delay paradigms in rabbits (Oryctolagus cuniculus) with either medial prefrontal cortex (mPFC) lesions or sham lesions. mPFC lesions of prelimbic cortex (Brodmann's Area 32) retarded EB conditioning in the trace but not the delay paradigm. However, this effect was significant only when the conditioned stimulus (CS) was 500 rather than 100 ms in duration. Lesions of the anterior cingulate cortex (Area 24) did not affect EB conditioning in a trace paradigm. Accompanying CS-evoked heart rate slowing was attenuated under all conditions by the mPFC lesions, although this result was not always statistically significant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal processing of information: The role of the medial prefrontal cortex and hippocampus: Theoretical comment on gilmartin and mcechron (2005).

M. R. Gilmartin and M. D. McEchron (2005) reported that single cells recorded in the prelimbic cortex of rats during the acquisition of trace fear conditioning display multiple patterns of neuronal firing during the trace. These finding are discussed in the context of the role of the prelimbic cortex in processing temporal information during trace conditioning and delayed matching- or nonmatching-to-sample paradigms based on both electrophysiology and lesion evidence. In addition, evidence is provided for a role of the hippocampus in supporting temporal processing of information and its potential interaction with the prelimbic cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of emotional responses in monkeys with rhinal cortex or amygdala lesions.

Four emotionally arousing stimuli were used to probe the behavior of monkeys with bilateral ablations of the entorhinal and perirhinal cortex. The monkeys' behavioral changes were then contrasted with those observed earlier (M. Meunier, J. Bachevalier, E. A. Murray, L. Málková, & M. Mishkin, 1999) in monkeys with either neurotoxic or aspiration lesions of the neighboring amygdala. Rhinal cortex ablations yielded several subtle behavioral changes but none of them resembled any of the disorders typically seen after amygdalectomies. The changes produced by rhinal damage took mainly the form of heightened defensiveness and attenuated submission and approach responses, that is, just the opposite of some of the most distinctive symptoms following amygdala damage. These findings raise the possibility that the rhinal cortex and amygdala have distinct, interactive functions in normal behavioral adaptation to affective stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the medial prefrontal cortex in the play fighting of rats.

Although decorticated rats are able to engage in play, their play is abnormal in three ways. First, decorticates do not display the normal, age-related shifts in defensive strategies during development. Second, decorticates do not modify their defensive tactics in response to the social identity of their partners. Third, decorticates display a global shift in defensive tactics from more complex to less complex strategies. It has been shown that lesions of the motor cortex (MC) selectively produce the abnormal developmental effects on play, and that lesions of the orbitofrontal cortex (OFC) selectively produce the deficits in behavioral discrimination between social partners. In the current set of experiments, we demonstrate that lesions of the medial prefrontal cortex (mPFC) produce the shift from more complex to less complex defensive tactics, while leaving intact the age-related and partner-related modulation of defensive strategies. Thus, we have evidence for a triple dissociation of function between the MC, the OFC, and the mPFC with respect to social play behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the role of medial prefrontal cortex dopamine receptors in cocaine-induced locomotor activity.

Medial prefrontal cortex (mPFC) dopamine (DA) modulates the motor-stimulant response to cocaine. The present study examined the specific mPFC DA receptor subtypes that mediate this behavioral response. Intra-mPFC injection of the DA D?-like receptor agonist quinpirole blocked cocaine-induced motor activity, an effect that was prevented by coadministration of the D2 receptor antagonist sulpiride. Intra-mPFC injection of the selective D? receptor agonist PD 168,077 or the selective D? receptor agonist SKF 81297 did not alter the motor-stimulant response to cocaine. Finally, it was found that an intermediate dose of quinpirole, which only attenuated cocaine-induced motor activity, was not altered by SKF 81297 coadministration, suggesting a lack of synergy between mPFC D?, and D? receptors. These results suggest that D? receptor mechanisms in the mPFC are at least partly responsible for mediating the acute motor-stimulant effects of cocaine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance-related activity in medial rostral prefrontal cortex (area 10) during low-demand tasks.

Neuroimaging studies have frequently observed relatively high activity in medial rostral prefrontal cortex (PFC) during rest or baseline conditions. Some accounts have attributed this high activity to the occurrence of unconstrained stimulus-independent and task-unrelated thought processes during baseline conditions. Here, the authors investigated the alternative possibility that medial rostral PFC supports attention toward the external environment during low-demand conditions. Participants performed a baseline simple reaction time (RT) task, along with 3 other tasks that differed in the requirement to attend to external stimuli versus stimulus-independent thought. Medial rostral PFC activation was observed in the baseline task and in a condition requiring strong engagement with external stimuli, relative to 2 conditions with a greater requirement for stimulus-independent thought. An important finding was that activity in this region was associated with faster RTs in the baseline task, ruling out an explanation in terms of task-unrelated thought processes during this condition. Thus, at least under certain circumstances, medial rostral PFC appears to support attention toward the external environment, facilitating performance in situations that do not require extensive processing of experimental stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)