Nominal Aphasia: Problems in Name Retrieval
It happens to all of us occasionally. As you walk down the hallway you see a familiar face—someone you have recently met—you reach into your brain expecting a complicated series of synaptic firing to bring forth the name person in front of you only to be disappointed. Although you know it is there in the recesses of your mind, you cannot summon the name of your new acquaintance. You settle instead for the ubiquitous nod and the word “hello”.
Where failure to occasionally recall the name of new acquaintance may feel uncomfortable, it typically does not create huge difficulties. For me this scenario happens all too often. Names of acquaintances and friends of less than a year’s duration frequently elude me at pivotal movements. Although my problem with name recall is worse for personal names, I also occasionally experience difficulties recalling the name of specific objects or “common names”. Indeed my friends and colleagues are familiar with me using the most round-about ways to identify specific people or objects. Physicians and psychologists have several clinical terms to describe this word-finding problem. Anomia is one general term for problems with word finding or recall that occurs with no impairment of comprehension or the capacity to repeat the words; the terms anomic and nominal aphasia are also used. (1)
My problem recalling names, both of people and of things, led me on an investigation of the mechanisms by which the brain stores and retrieves this information, and how names are stored and summoned. I was also particularly interested in how malfunctions in the brain’s name retrieval system arise when there has been no physical trauma.
It is important to understand that articulating names is merely the final stage in a series of complex processes. Before names can be retrieved from the brain, they must be learned and stored. There are three different components of memory: immediate/sensory memory, short-term memory (including working memory—memory that consists of information held in the mind for a brief time for a specific purpose), or long-term memory. (2) Sensory memory is our “initial memory”. It lasts for approximately half a minute. It is during this critical stage that information must undergo additional processing in order for it to become fixed in the brain’s short-term memory. Attention is critical to facilitating the movement of information from sensory memory to short-term memory. (2) (4) (7) Once information is lodged in short-term memory several things may happen: it can be maintained in short-term memory; it may be encoded in long-term declarative memory by linking this newly acquired information to existing knowledge; or it may leave short-term memory and the brain altogether because of disuse and lack of attention.
Retrieving information or names from this process similarly involves a complex series of steps and pathways. Specialists characterize the following fundamental stages of the name retrieval process as conceptual preparation, followed by word generation proceeding through lexical selection, morphological and phonological encoding, followed by vocal articulation. More simply, the process of retrieval can be understood as a movement of information from long-term memory to short-term memory and subsequent articulation. The aid of neuroimaging tools makes it is clear that it is faulty to localize the retrieval of proper names to one portion of the brain. Like vision, proper name retrieval is better understood as a distributed system in which large portions of the left hemisphere are involved. In the same way that the ‘picture’ we hold in our heads is a result of a pattern of visual activity in the neocortex, we store proper names in the left hemisphere of our brain. (3)
With this sketch of name retrieval in mind, we can begin to anticipate where difficulties in name retrieval may arise. Anomia may arise from failure of information to progress from sensory memory to short-term or long-term memory. This explanation is consistent with the advice of popular memory improvement strategies to improve memory. For example, Harvard Medical Guide to Optimum Memory, Dr. Gary Small’s Memory Prescription, and the School of Phenomenal Memory’s GMS Manual, all emphasize strategies for fixing memories in the brain through the focusing of attention. (3) (4) (6) Attention, in this context, can be understood as a conscious decision to move information from sensory memory to more durable forms. Initially this emphasis on attention with regard to names may incorporate the I-function, as the individual knowingly keeps a name in working or short-term memory.
Difficulties may also arise in name retrieval if names have been improperly encoded in the long-term memory. The encoding of names into declarative (a type of long-term) memory may be particularly “tricky” in that this process may occur both intentionally—that is, with the I-function—or unintentionally—without the I-function. If connections and linkages have not been made between nearly learned names and existing knowledge, name retrieval will be difficult if not impossible. Therefore, the encoding of names in the long-term memory requires a retrieval of existing information in the long-term from which the brain makes connections and linkages. (2) The consolidation of names is facilitated by the hippocampus which allows for the rehearsal of information of names in a sequence of events that is mentally replayed and rehearsed in order to strengthen pathways of neuronal activity.(3)
"Blocking" is one difficulty that may arise in moving information from long-term declarative memory to working memory for recall. According to Dr. Aaron Nelson, author of the Harvard Medical School Guide to Achieving Optimum Memory, the tip-of-the-tongue phenomenon can be attributed to this action. In blocking, Nelson argues, we are unable to recall a specific memory because another memory is standing in the way. The problem lies not in memory storage but in an intrusive obscuring memory. “The harder you try to peer around this interloper, the more insistent it becomes at forcing its way into your consciousness. You know it is the wrong answer and part of you knows the right answer, but you can’t think of it because the wrong answer is in the way”.
Understanding the mechanisms involved in name-finding, inspire us to localize the process by which proper and common names are stored. With this aim, researchers in the past have relied heavily on the examination of patients with lesions and other physical trauma to known portions of the brain who have suffered from nominal aphasia. However, many of these patients have also suffered a number of other neurological problems, reducing the ability to exclusively cause to nominal aphasia.
More recently researchers have taken advantage of the ready availability of imaging technologies such as functional magnetic resonance imaging (fMRI)—which enables researchers to map neuronal activity in the brain—and the measurement of event-related potentials (ERPs) from electrodes placed on the head of participants recognizing new faces and identifying familiar ones. Research suggests that when an individual views a recently learned face, a response is triggered in the brain that reactivates distributed cortical networks linked by hippocampal connections. (9) Specific regions in the left hemisphere such as the left hippocampus, and large medial temporal region demonstrate stronger associations with name memory. Yet, other regions of the brain also demonstrate an impact on name recall. For example, left-sided lesions in basal ganglia, the occipital lobe and the thalamus—all brain structures outside of the temporal lobe—have also been connected to proper name anomia. (3)
Ultimately, a definitive answer to the causes behind my anomic problems still eludes me, much as a name fails to appear on my lips. There is no easy explanation for why certain names are forgotten only at certain moments rather than others. Certainly factors which negatively impact health and well-being generally can affect memory. Genes, hormones, stress, sleep, alcohol, exercise, diet, and age for example can all impact name recall. Training my brain to participate in strategies that engage me and focus my attention on the names of recently acquainted individuals offers the best hope of improvement. Connecting new people to existing knowledge and categories in my brain offers the best prescription. If we compare the memory of names to a network of insulated cables—some perhaps more poorly insulated than others—we can forge news lines and associations that can remove those names from the tip of my tongue into the output signals my acquaintances recognize as their name.
(1) http://neurology.health-cares.net/nominal-aphasia.php, Health Cares
(2) http://www.muskingum.edu/~cal/database/general/memory.html#, System Learning Strategies Database—Muskingum College
(3) Semenza, Carlo. Retrieval Pathways for Common and Proper Names. Cortex, (2006) 42, 884-891
(4) Nelson, Aaron P and Susan Gilbert. Harvard Medical School Guide to Achieving Optimum Memory. New York McGraw Hill 2005.
(5) Small, Gary and Gigi Vorgan. The Memory Prescription: Dr. Gary Small’s 14-Day Plan to Keep Your Brain and Body Young. New York: Hyperion Books. 2004
(6) http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1486764, National Institute of Health article “Spaced Retrieval System of Anomia”
(7) http://www.pmemory.com, GMS Manual: School of Phenomenal Memory
(8) http://www.tbiguide.com/memory.html, Traumatic Brain Injury Survival Guide.
(9) Ferreira, Fernanda et al “A theory of lexical access in speech production.” Behavioral and Brain Sciences (1999) 22, 1-75.
(10) http://www.learnmem.org, “Neural Correlates of Person Recognition” Learning and Memory.