An Investigation of Patients with Macroanatomical Brain Lesions
In 1888, Leonore Welt, a Swiss physician, reviewed a series of patients with damage to the frontal cortex, who showed marked changes in moral character as judged by their jocular childish or aggressive behavior (Welt, 1888). Interestingly, their general intelligence was preserved. Phineas Gage, the now famous US American patient (Damasio et al., 1994), with an iron-bar injury to his medial frontal lobes was one of the cases reviewed by Dr Welt. Based on postmortem neuropathology and injury pattern, she concluded that the most consistent structure damaged in all cases was the right medial orbitofrontal cortex.
While this was probably the first systematic evidence for a causal role of specific brain structures for enabling moral behavior, it also marked the beginning of a controversy about the function of the frontal lobes. This is because systematic studies of patients with head injuries during the First World War confirmed earlier case reports of some patients with frontal lesions and no behavioral change (Teuber, 2009). This lack of impairment in some patients could of course be explained by insufficient characterization of the lesion or lack of sensitivity of clinical observation. However, it could also point to individual variability in cognitive-anatomical architecture leading some patients to be more sensitive than others to frontal brain lesions.
In the 1980s, brain computed tomography became available in clinical settings and led to a renaissance of neuropsychological case studies. Eslinger & Damasio sparked new interest in the neural basis of behavior counter to moral rules by describing EVR, a patient with ventral frontal lobe damage due to tumor resection (Eslinger and Damasio, 1985). He exhibited difficulty in making daily life decisions and made choices that led to a ruin of his financial fortunes as well as his marriage. At the same time, he showed normal functioning on classical tests of executive functioning such as the Wisconsin Card Sorting test, which is usually impaired in patients with left dorsolateral frontal lesions, which was not damaged in EVR.
In the same decade, a neurodegenerative disease, originally described by Arnold Pick in the late nineteenth century, became recognized as a relatively common form of early-onset dementia that could be reliably diagnosed before death (Snowden et al., 2001). These patients exhibited varying degrees of frontal and anterior temporal atrophy captured in the term ‘frontotemporal lobar degeneration.’ This led to cumulating evidence on inappropriate social behavior in these patients (Bozeat et al., 2000) that was independently associated with right anterior temporal and ventromedial frontal atrophy (Liu et al., 2004). Patients with right anterior temporal lesions behave as inappropriately as patients with ventral frontal atrophy. For example, in their clinic, the authors saw a patient (further referred to as ‘the singing lady’) with isolated right anterior temporal lobe atrophy, who lost her job, because of kissing and singing to customers at work, who also sang happy birthday to her parents on the cemetery.
Studies in patients with brain lesions were often hampered by the lack of neuropsychological tasks that could probe cognitive functions relevant to the observed behavioral changes and largely relied on carer reports. Loss of guilt was reported by carers of patients with ventromedial (prefrontal cortex) lesions (Koenigs et al., 2007) and neurodegeneration in this area, which included the subgenual cingulate cortex, was associated with loss of interpersonal warmth as judged by carers (Sollberger et al., 2009). Inappropriate behavior in these patients often goes against societal needs or needs of others and therefore clearly has moral implications. However, the disruption of which cognitive and emotional components leads to this behavioral change is disputable. Patients with ventral frontal lesions were found to show intact social knowledge when asked about their behavior (Saver and Damasio, 1991; Eslinger and Damasio, 1985). Similarly, Mendez et al. found in their patients with frontotemporal lobar degeneration that knowledge of moral rules was intact when assessed on a questionnaire, but nevertheless patients failed to act on these rules (Mendez et al., 2000). This may lead to the hypothesis that moral motivation and knowledge may be at least partly dissociable. The hypothetical causes of socially inappropriate behavior are
1) Loss of (access to) knowledge of appropriate social behavior (Zahn et al., 2009b).
2) Loss of the moral motivation to act upon intact social knowledge (Moll et al., 2005b).
3) Loss of the ability to suppress urges/drives (Brutkowski, 1965) with intact social knowledge of their inappropriateness and intact moral motivation to act upon this knowledge.
In order to test these different possibilities, one needs to probe moral motivations experimentally while controlling for social knowledge and vice versa. Two studies in patients with frontotemporal lobar degeneration have used this approach. One study showed that patients with damage of the right anterior temporal lobe displayed selective deficits on abstract knowledge of social behavior (i.e., social conceptual knowledge, e.g., what it means to act ‘tactfully’) relative to nonsocial conceptual knowledge (e.g., what it means to be ‘nutritious,’ Zahn et al., 2009b). Furthermore, selective deficits on social concepts were associated with inappropriate social behavior. The social concept discrimination task used to probe this particular type of social knowledge did not require moral motivations and controlled for the effects of positive or negative emotional valence. Interestingly, the right anterior temporal lobe atrophy patient, ‘the singing lady,’ exhibited a selective impairment on social concepts with relatively intact nonsocial concepts when using this test (Zahn et al., 2012).
Another study showed that patients with frontotemporal lobar degeneration and relatively stronger involvement of the septal area were selectively impaired on a task probing guilt and pity, relative to other negative emotions such as embarrassment, disgust, and anger (Moll et al., 2011). The task controlled for the degree of social knowledge required by using similar statements to describe social situations in which one usually feels a particular moral feeling (e.g., “Your mother calls you one night, telling you she was not feeling well. You did not take her seriously and the next day she died” associated with guilt in 80% of a normative sample). Neurodegeneration of the frontopolar cortex was associated with selective loss of guilt, pity, and embarrassment compared with disgust and anger.
These studies, together with evidence from fMRI reviewed below, indicate that moral motivations and social conceptual knowledge are associated with dissociable brain regions and can thus independently contribute to inappropriate social behavior. The third and most popular explanation for such behavior, however, is that these patients know about other people’s needs and are motivated to act on them, but that they have lost the ability to suppress selfish urges in subcortical regions that counteract their ability to act morally.
This frontal-subcortical suppression view probably became influential because of the way conditioning experiments in nonhuman animals were interpreted (Brutkowski, 1965). To the authors’ knowledge, there is, however, no anatomical evidence supporting strictly unidirectional, inhibitory connections from frontal cortical to subcortical areas, which would support such a suppression mechanism. Furthermore, there is no evidence that selfish motivations are more dependent on subcortical than cortical mechanisms. On the contrary, there is evidence from case reports in patients with subcortical lesions that these may be associated with severe antisocial behavior. Subcortical lesion cases included hypothalamus, septal area, amygdala, and basal ganglia (Moll et al., 2003), but it is unclear how regularly these associations can be found. A more plausible version of the frontal-subcortical suppression model is mentioned below in which the frontal cortex is thought to control (Miller and Cohen, 2001) rather than suppress other areas of the brain.
In principle, one must consider another explanation for ‘immoral’ behavior after ventral frontal lesions, namely, that moral behavior requires more complex cognition and will thereby be nonspecifically impaired in large brain lesions. If this was the case, patients with similar degrees of brain damage and impairment should also show similar degrees of deviations from moral behavior. Interestingly, this is clearly not the case in that patients with Alzheimer’s dementia in similar mild to moderate stages of the disease do show intact interpersonal behavior in the overwhelming majority of cases (Bozeat et al., 2000). Alzheimer’s dementia typically leads to neurodegeneration of medial temporal, as well as medial and lateral parietal brain regions in these stages (Herholz, 2003). This means that moral behavior in a daily life context appears to be independent of these brain regions.
Learn more about the functional neuroimaging of moral cognition and emotion, cognitive-anatomical models of moral cognition and emotion, and implications for differential vulnerability in psychiatry here.
This excerpt is taken from Neural Foundation of Morality by Roland Zahn, Ricardo de Oliveira-Souza and Jorge Moll. The article examines the neuroscience behind the complex and sophisticated behavior of morality and investigates how it can be used to improve the understanding of associated neuropsychiatric conditions.
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