The Neurological Behavioral Examination

MOTIVATION AND EMOTION

Motivation. Motivation describes the intensity and persistence in working toward a goal. Motivation requires emotional responsivity, executive functions, and “auto-activation” collaborating in a motivation-action-reward loop involving prefrontal cortex (dorsolateral; anterior cingulate) and basal ganglia (dorsal caudate, internal globus pallidus, substantial nigra, ventral striatum, ventral pallidum). Apathy and abulia are disorders of diminished motivation and important manifestation of brain disease. Apathy (“without passion”) is prominently decreased emotional responsivity with a lack of emotional expression or interest in activities. Clinical conditions associated with apathy include anosodiaphoria (lack of concern for an acknowledged disorder), anosognosia (lack of knowledge for a disorder), alexithymia (inability to identify one’s emotions), and “stuporous” catatonia (unresponsive, mute, immobile with inappropriate or prolonged postures or body positions into which they are placed [“cataplexy”]). In contrast to apathy, abulia (“without will”) is a primary loss of initiation from executive dysfunction and autoactivation (self-initiation). Clinically, examiners have difficulty distinguishing abulia from apathy. Compared with apathy, abulia appears more severe, results from frontal cognitive impairment rather than primary emotional hyporesponsivity, and melds into akinetic mutism with absent spontaneous movements or speech beyond occasional words or short phrases (see Chapter 7 ).

Emotion. Many definitions of emotion view it as a type of motivation aimed at promoting adaptive behavior. Emotional experiences are subjective “feelings” associated with somatic-autonomic nervous system arousal. There are much data showing that the somatic-autonomic activity for emotional experiences vary greatly. This, along with the cognitive appraisal or interpretation of emotions, challenges the view that specific emotions originate from specific brain regions. Nevertheless, there is evidence for the reconstitution of somatic states in ventromedial prefrontal cortex when exposed to certain types of experiences. There is also some support for both right hemisphere dominance for emotions and the valence theory attributing negative emotional tendencies to the right hemisphere and positive emotional tendencies to the left. Two important components of emotion that can be disturbed in patients are mood and affect. Mood is the patient’s subjective feelings, whereas affect is the outward expression of emotion, such as withdrawn expression, poor eye contact, and tearfulness. Mood and affect are not necessarily congruent and can be dissociated as in pseudobulbar palsy in which excessive affect may not reflect the quality and extent of the underlying mood.

SOCIAL BEHAVIOR

A number of brain regions participate in social behavior and can be disturbed from brain disease. Social propriety and interactions can be profoundly altered with mesial frontolimbic lesions, as exemplified by John Harlow’s description of Phineas Gage, perhaps neurology’s most famous patient ( Fig. 14.1 ). Gage’s behavior was dramatically changed after an accident propelled an iron rod through his brain damaging his ventromedial prefrontal areas. Subsequently, he became, in the words of John Harlow, “...fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires….[with] the animal passions of a strong man…” Gage’s behavioral changes illustrate how the mesial frontal lobes (ventromedial, orbitofrontal) are particularly involved in human social behavior. The ventromedial prefrontal cortex attributes meaning to social phenomena and related areas determine the socioemotional significance of percepts (anterior insulae, anterior cingulate cortex, amygdala, anterior temporal cortex). Many neurological illnesses have prominently disturbed social tact and manners, disinhibition, and inability to comply with social norms consequent to lesions or disease in these regions ( Table 14.1 ).

The examiner assesses social cognition not only from observation of social behavior but also through tests of Theory of Mind, empathy, and social perception. Theory of Mind is the ability to represent the thoughts, beliefs, attitudes, and feelings of others. It involves the ventromedial prefrontal cortex, amygdala and anterior temporal pole, posterior superior temporal sulcus, precuneus, and the right temporoparietal junction. There are different subtypes of Theory of Mind, including cognitive understanding, affective understanding, and first- or second-order levels. With regard to empathy, there is no universally accepted definition. Most agree that empathy is the ability to identify with the emotional experience of (“feeling as”) others in a prosocial way. It involves an evaluation of the experience of others, which leads to the creation of a model in one’s mind of another’s feelings. The experience of empathy facilitates sympathy (“feeling for”) for others and prosocial behavior (responding compassionately). An aspect of “cognitive empathy” is perspective taking, which involves the dorsal mid anterior cingulate cortex, adjacent dorsomedial frontal cortex, and ventromedial prefrontal cortex. An aspect of “emotional empathy” is affect sharing, which involves the anterior insula and inferior frontal gyrus (right frontal subgenual and right temporo-limbic). Finally, social perception for faces, body, and other signals of emotion are an additional critical part of navigating the social world. Most of these overlaps with perception, as described in Chapter 10 , with special emphasis on the ability to recognize facial emotions.

PSYCHOPHYSIOLOGICAL BEHAVIORS (INCLUDING AGGRESSION)

Broadly defined, psychophysiological behaviors involve the hypothalamus and related areas, which regulate the sleep-wake cycle, the sexual drive, hunger and satiety, thirst and drinking, and aggressive behavior. Inappropriate or increased sexual behavior may be manifestations of brain disease, either from primary hypersexuality or from sexual disinhibition. In primary hypersexuality, there are recurrent and intense sexual fantasies, urges, and risky behaviors, often associated with repetitive but unsuccessful efforts to reduce or control these sexual symptoms. Primary hypersexuality has occurred with strokes and surgical resections for epilepsy, tumors, or right temporal variant frontotemporal dementia from temporal-amygdalar damage and a release of sexual arousal. Far more commonly, inappropriate sexual behavior results from sexual disinhibition as part of a frontally mediated general disinhibition. These patients react impulsively and opportunistically to tempting environmental situations involving sexual or other objects of interest, without necessarily following-through or consummating their sexual behavior.

Changes in dietary and eating behavior from brain disease include a spectrum from alterations of dietary preferences to the placement of nonfood or inedible items in their mouths. Basic food intake is under hypothalamic control, with a lateral region controlling feeding and a medial region controlling satiety; however, complex changes in eating behavior are more commonly associated with right frontal and temporal lobe damage rather than with hypothalamic lesions. Excessive eating (hyperphagia) is a significant feature, not only of neurological conditions, such as behavioral variant frontotemporal dementia, the Klein–Levin syndrome, and the human Klüver–Bucy syndrome, but also of developmental disorders, such as the Prader–Willi syndrome. Patients with frontotemporal dementia syndromes may have cravings for sweets or carbohydrates or obsessions for particular foods. In addition, disease in the orbitofrontal region may impair the ability to refrain from taking food or to respond to feelings of satiety.

Aggression is someone’s action that intentionally delivers something unpleasant, either psychological or physical, to another. Violence is an extreme form of aggression that involves physical action. There are two major types of aggression: 1) reactive or affective aggression, which is an emotional, often explosive, response to a perceived threat or provocation; and 2) instrumental or predatory aggression, which is controlled (organized), purposeful (premeditated), and may be used to achieve an antisocial goal. The hypothalamus and periaqueductal gray of the midbrain (connected to amygdala and prefrontal cortex) control the expression of both behavioral and autonomic components of aggression. Reactive aggressive is associated with abnormalities in the hypothalamic–pituitary–adrenal axis, as well as in serotonin and catecholamine neurotransmitters. Reduced control from the prefrontal cortex, in particular its medial and orbitofrontal portions, is associated with instrumental as well as reactive aggression. In addition, investigators have reported smaller and more hypofunctional amygdalae among chronic violent offenders.