By Thierry Harris
Interdisciplinary research across McGill — including the Bloomfield Centre for Research in Aging, the School of Communication Sciences and Disorders and the Centre for Research on Language, Mind and Brain—is exploring how language works… or doesn’t.
As young children move through their early years, their command of language undergoes an incredible growth spurt. Vocabularies swell. Sentence construction becomes increasingly elaborate. It becomes easier to navigate those areas — such as sarcasm or irony — where the unspoken speaks louder than the words themselves. And, although we never again enjoy such amazing rates of improvement, our language skills do tend to keep on getting better — after all, unless we’re hermits, we’re constantly honing our language skills.
But, sometimes, aging has other ideas—and words fail us.
Howard Chertkow, Director of the Bloomfield Centre for Research in Aging at the Lady Davis Institute for Medical Research, is sitting in his office at the Jewish General Hospital looking at pictures of a bear and a hippopotamus. “When I show a bear to a patient with Alzheimer’s disease, they’ll say it’s a dog. A hippopotamus, that’s a pig.”
People suffering from Alzheimer’s dementia often have difficulty remembering words and, as in Chertkow’s example, regularly call things by the wrong name. It’s one way that the aging process can complicate speech and communication,things most of us take for granted.
Chertkow’s research focuses on the impact of dementia (Alzhemier’s-induced and otherwise) on semantic memory,the brain’s long-term storage of concepts, words and meanings. Using brain imaging technology, he’s attempting to understand the structure of language in the “normal” brain. By finding the location—or, perhaps, locations — of semantic memory, and learning how it is organized, he hopes to relate physical changes in the brain to cognitive difficulties — and, with any luck, to develop therapies for improving the cognition of dementia patients.
In the past ten years McGill has seen a significant increase in cross-faculty, interdisciplinary research partnerships to study the mind and how language works. “There is a very strong neurology group and cognitive neurologists interested in language disorder,” says Chertkow. “Through our teaching hospitals, we have access to patients. The Montreal Neurological Institute provides both imaging technology and expertise. So we’ve got cognitive neurology, we’ve got brain imaging, and we’ve got the basic brain and language scientists all in the same place with the potential to interact in multiple ways.”
As with many afflictions, early detection is important — and Chertkow’s seemingly simple tests with animal pictures provide an early warning of language problems.
“Animals are particularly difficult for people with Alzheimer’s disease, because they have no particular function. So the system for distinguishing animals is pretty sophisticated and is quite likely to break down early on when you get damage to these areas,” says Chertkow.
Chertkow sees new therapies opening up for older people suffering from Alzheimer’s disease once the early warning signs appear. “We are finding that there are areas of the brain that are affected in Alzheimer’s disease such as the temporal lobe. But other parts of the brain, such as the parietal lobe, are not only preserved, but can compensate for the compromised areas.” This compensation, known as cognitive reserve, may be improved through therapies such as trans-cranial magnetic stimulation, a procedure that uses electromagnetic induction to generate a painless electric current across the scalp and skull. “If we stimulate these compensatory areas they actually seem to improve patient’s picture naming,” says Chertkow.
Cognitive reserve capacity may also improve through training. Shari Baum, James McGill Professor at the School of Communication Sciences and Disorders (SCSD) and former founding director of the Centre for Research on Language, Mind and Brain (CRLMB), and Debra Titone of McGill’s Department of Psychology are studying executive functions with bilingual older adults. Executive functions are a collection of processes which deal with things like pursuing a goal, inhibiting distracting information and maintaining knowledge and working memory to store things in your immediate consciousness and manipulate them in various ways. As we get older, these functions decline. Baum and Titone are building on research by Ellen Bialystok of York University in Toronto, who has suggested contentiously that bilingualism effectively acts as weight training for executive functions—and may stave off the onset of Alzheimer’s dementia by as much as four years.
Titone and Baum, along with Denise Klein, a clinical research scientist from the Montreal Neurological Institute, recently received a CIHR grant to study further the effects of aging and bilingualism. “Much of the literature on aging, and age-related changes in communication and language, uses probes or measures of language processing that maybe lack nuances and sensitivity,’’ says Titone. Her team will instead gauge language comprehension by measuring eye movement using an eye tracker, which tracks pupil fixation. Eye movement has “exquisite temporal resolution,” meaning it is sensitive to the real-time processing of language, which happens on the order of milliseconds; it is an excellent measure of whether someone is understanding what is being said.
Facts about aging:
Alzheimer’s disease is the cause of 63 per cent of all dementias. The Alzheimer Society of Canada estimates this number may increase to 68 per cent by 2034.”
Baum doesn’t just explore problems understanding words, either: She’s also researching why some older adults have difficulty recognizing key changes in intonation, rhythm and phrasing. Such prosodic processing deficits can result in severe misunderstandings. Take, for example, the sentence “John said Mary was the nicest girl at the party.” Without appropriate prosody, it’s difficult to determine whether John made his comment at the party, or was distinguishing Mary’s shining qualities from those of all the other girls at the party. “Intonational cues disambiguate the sentence,” she says, “but if you have an impaired ability to understand prosodic cues, you may misinterpret the meaning of the sentence.” With funding from two CIHR grants, Baum and Karsten Steinhauer, a neurobiology professor in the CRLMB, are using event-related potential (ERP) measurement techniques to understand what exactly goes wrong when such problems occur. By making electro encephalography (EEG) recordings of the brain’s electrical activity while a person is listening to speech, ERP measures millisecond-by-millisecond information about how prosodic cues change the way in which that person processes a spoken sentence. “One potential misconception is that older people may simply miss the prosodic cues because of hearing deficits,” says Steinhauer, “but our research, along with that from other labs, suggests otherwise. Adults aged 65 to 80 years vary a lot in how they interpret, or rate the meaning of, spoken sentences. Difficulties, or differences compared to young adults, may not be due to problems in perceiving prosodic patterns. For these early processing stages, our ERP data show very similar brain signatures in young and older adults.” On the other hand, Steinhauer’s team found ERP evidence that the aging brain may have problems integrating prosodic patterns with other types of information, such as the sentence structure.“As these difficulties occur at later processing stages and partly rely on memory capacity,” Steinhauer concludes, “this may explain why people with Alzheimer’s often struggle with prosodic processing as well.”