There is a difference between the surface-level knowledge of a word or concept, and deep, rich meaning. Shallow word knowledge enables one to name a picture or provide a simple 3- or 4-word definition to a target word. Deeper mastery involves the amount of information associated with a word – different senses of the word, the number of features of a concept, other words the target is associated with in language use.
I used measures of semantic richness to document previously unreported deficits in patients with hippocampal amnesia. Previously acquired, remote semantic knowledge has been considered intact in hippocampal amnesia However, on more sensitive measures, the patients’ knowledge was severely impoverished. While their surface level knowledge was intact, patients had much less information associated with common words than healthy and brain damaged comparison participants. They could provide fewer features and senses to target words and could identify far fewer correctly matching word associates. These findings suggest a role for the hippocampus in updating what we know about a concept with new information. We are constantly learning new things about the world, are constantly updating our knowledge, and these abilities are supported by the hippocampus and greater medial temporal lobes.
Figurative language – metaphor and analogy – play major roles in cognition and communication. One of the best ways to communicate an idea, or to teach someone something new, is to describe the idea in terms of another, more familiar idea by using a metaphor or an analogy. Despite the importance of figurative language in our thinking and our communication, there is a lot we don’t know about how the brain supports these abilities. Scientists are still debating which parts of the brain support the comprehension of a metaphor. We don’t know how figurative language is affected in healthy aging or in age-related neurodegenerative disease. I’ve used measures of metaphor comprehension to document impairments in patients with left-hemisphere neurodegenerative disease. This work points to the crucial role that left-hemisphere regions play in normal metaphor comprehension.
Sensitive measures of cognitive decline in the earliest stages of Alzheimer’s disease (AD)
Scientists have discovered that the pathological processes in AD, the buildup of abnormal proteins in the brain, begin years to decades before patients show impairments on standard assessments of memory and language. Expensive brain scans can measure the buildup of these proteins. Could more sensitive measures of cognition detect cognitive change earlier than standard tools? I am testing older adults that perform well on standard tests of memory and language on my own tests of semantic richness, metaphor, and analogy that we predict will be more sensitive. We can relate performance on these sensitive tests to the presence of abnormal proteins seen in AD and to atrophy of brain areas that are first affected in the AD trajectory. These sensitive tools can track cognitive change in AD, perhaps leading to earlier diagnoses, and could help evaluate the effectiveness of potential pharmaceutical or life-style interventions.