ANALYSIS AND COMMENTARY Amnesia and Crime: A Neuropsychiatric Response Hal S. Wortzel, MD, and David B. Arciniegas, MD Bourget and Whitehurst’s “Amnesia and Crime,” published in a prior issue of the Journal, addresses a conceptually complex and clinically challenging subject. Their treatment emphasizes psychiatric conditions in which memory disturbances may arise that are relevant to criminal proceedings. However, their consideration of the neurobiology of memory, memory disturbances, and the neurobiological bases of interactions between psychiatric symptoms and memory merit further elaboration. The relevance of memory impairment to criminal matters requires forensic psychiatric experts to possess a basic understanding of the phenomenology and neurobiology of memory. The present authors describe briefly the phenomenology and neuroanatomy of memory, emphasizing first that memory is not a unitary cognitive domain, clinically or neurobiologically. The assertion that psychotic delusions produce memory impairment is challenged, and the description of “organic” amnesia, both semantically and in terms of its clinical features, is reframed. Resources on which to build a neuropsychiatric foundation for forensic psychiatric opinions on memory impairment surrounding criminal behavior are offered. J Am Acad Psychiatry Law 36:218–23, 2008 The neurosciences are developing rapidly. While thors’ thoughtful synthesis of this exigent topic is to there is still much to be learned, considerable ad- be highly commended, we offer here some observa- vances have been made in defining the neurobiology tions on this work from a neuropsychiatric perspec- that underlies cognition, emotion, and behavior. tive and discuss their implications for the practice of Among the cognitive domains, memory stands out as forensic psychiatry. a function that has been highly investigated, yielding Bourget and Whitehurst,1 near the end of their many fruitful insights into its nature, as well as the paper, indicate that an in-depth review of the neuro- neuroanatomy and neurochemistry that make this psychology and neuroanatomy of memory is beyond vital cognitive function possible. With this back- the scope of their article. We agree that an in-depth ground in mind, we read with great interest Bourget review of this subject is an undertaking of enormous and Whitehurst’s article, “Amnesia and Crime.”1 scope. Nevertheless, readers of this journal interested The authors clearly identify a concern of vital impor- in the topic of amnesia and crime may benefit from tance to forensic psychiatric practice. Indeed, the an additional review of the phenomenology and neu- evaluation of reported amnesia, particularly among robiology of memory and memory impairments. criminal defendants, is very challenging and requires a precise approach to the assessment of memory and Key Concepts in the Phenomenology an understanding of its neurobiology. While the au- of Memory Dr. Wortzel is Instructor-Fellow, Veterans Integrated Service Network At the outset, it is important to acknowledge that 19 Mental Illness Research, Education, and Clinical Center (VISN 19 memory is neither a unitary concept nor a single MIRECC), Denver Veteran’s Affairs Medical Center, and the Neu- 2,3 robehavioral Disorders Program, Department of Psychiatry, Univer- neuropsychological function. The term memory is sity of Colorado School of Medicine, Denver, CO. Dr. Arciniegas is generally used to refer to the ability to learn, store, Director of the Neurobehavioral Disorders Program and Associate Professor of Psychiatry and Neurology, University of Colorado School and retrieve information. However, there are several of Medicine, Denver, CO. Address correspondence to: Hal S. Wortzel, different, albeit sometimes overlapping and interre- MD, Department of Psychiatry, CPH Room 2508, 4200 East 9th Avenue, C268-25, Denver, CO 80262. E-mail: hal.wortzel@ lated, ways of categorizing memory. Such categoriza- uchsc.edu tion is generally based on the type of information 218 The Journal of the American Academy of Psychiatry and the Law Wortzel and Arciniegas learned and retrieved, as well as the duration of the when the interval between learning and recall they interval between learning and retrieving. denote is not stated explicitly by the writer or speaker With regard to the type of information learned, using them. two general categories of memory are well accepted: explicit (or declarative) and implicit (or procedural). The Neuroanatomy of Memory in Brief Declarative memory refers to the ability to learn, en- Declarative memory requires first an intact sensory- code, and retrieve factual (semantic) information, as cortical pathway through which to acquire (learn) well as information regarding events (episodic) or new information. From primary and secondary asso- oneself (autobiographical). In other words, explicit ciation cortices, highly processed multimodal memory pertains to who, what, where, and when. sensory information is transmitted from parietal het- This domain of memory is also sometimes divided eromodal association cortices to the entorhinal-hip- into spatial and verbal subcategories, with spatial pocampal complex. When that incoming multimo- memory denoting the learning, storage, and retrieval dal sensory information produces a sufficiently of visuospatial information and verbal memory de- robust signal in the hippocampus (a process that, at noting the learning, storage, and retrieval of verbal- least in part, necessitates amygdala-hippocampal in- linguistic information. Declarative memory is highly teractions that attach a motivational/emotional, or associative and subject to representational flexibility “survival-related,” valence to that information), the (and hence to post hoc modification or error). process of long-term potentiation (LTP) within the Implicit, or procedural, memory denotes the abil- network processing that information is initiated. By ity to learn, store, and recall (by action) skills and forming stable synapses within that network, LTP, a procedures, as well as some other nondeclarative sen- glutamatergically mediated and cholinergically de- sory events. It generally denotes memory for “how” pendent process, serves as the neural basis for encod- things are done, and is demonstrated by execution ing.4,5 Because the hippocampus is necessary for en- rather than by explanation. Learning in this context coding declarative information, the process of new implies the tuning and modification of task-related learning of declarative information is described as sensorimotor systems (e.g., how one’s fingers are hippocampally dependent. moved when playing a violin) rather than the encod- The processing stream into which the hippocam- ing of task outcomes (e.g., the song played by that pus projects via the hippocampal-forniceal-mamillo- series of movements). As a result, procedural mem- thalamic pathway extends to the frontal areas (and ory is neither associative nor flexible, and its retrieval particularly the dorsolateral prefrontal cortex) in- is limited to the context in which it was acquired (i.e., volved in the process of consolidating new memories. actually playing a violin, as opposed to playing an- After consolidation, volitional retrieval of declarative other stringed instrument or “air violin”). Both con- information requires prefrontal structures to activate ceptually and clinically, retrieval of procedural mem- the selective distributed networks in which that in- ory overlaps considerably with praxis, the execution formation was originally encoded. In contrast to new of a skilled purposeful movement on demand. learning, volitional retrieval of previously learned With regard to the duration between learning and (consolidated) information is not hippocampally de- recall, there are several temporally based types of pendent, but is instead frontally dependent. This memory. Working memory describes the process of type of memory is highly associative: reactivation of keeping information in mind or on-line for short- nearly any part of the network involved in the origi- term use in processing additional information and nal encoding of that information, or activation of overlaps both conceptually and nosologically with other networks whose constituent elements are immediate memory. Short-term memory refers to shared by the network involved in the original encod- the ability to retain information for a period of sev- ing of that information, will result in automatic eral minutes to a few days, and long-term memory (nonvolitional) retrieval of that information. refers to the retention of information over a period of In general, encoding and retrieving verbal-linguis- days to years. Unfortunately, the interval between tic declarative information is a left (dominant) hemi- learning and recall denoted by short- and long-term sphere function. Nonautobiographical episodic memory varies among studies. Accordingly, these memory appears to engage both hemispheres,6 terms are potential sources of nosological confusion whereas spatial memory and autobiographic declar- Volume 36, Number 2, 2008 219 Amnesia and Crime ative memory appear to be relatively, but not exclu- mation acquired proximate to the time of onset of sively, more strongly lateralized to the right hemi- memory dysfunction is more severely affected than sphere. These latter two types of memory also appear information acquired more remotely (Ribot’s law). to engage specific additional neuroanatomic areas. In In other words, events immediately preceding