Tag: Cognitive

Different Types of Leukoencephalopathy

Cynthia A. Lockley on
  • Arteriolosclerotic Leucoencephalopathy in the Elderly (ALE) from the National Library of Medicine (NIH). ALE is characterized by white matter lesions associated with atherosclerosis and arteriolosclerosis. Mild lesions are focal and probably represent early status cribosus or incomplete lacunar infarcts.

    ALE is common in old age and is probably the cause of leuko-araiosis in most CT scans in the elderly. ALE may be asymptomatic. The severity of white matter changes may not be related to the severity of neurological deficit. Multiple lacunar infarcts or associated degenerative diseases (i.e., Alzheimer's disease) may be the main cause of dementia in patients with ALE.

  • "Leukoencephalopathy in Patients With Ischemic Stroke" by J. Bogousslavsky, M.D., F. Regli, M.D., and A. Uske, M.D. Stroke 1987 Sep-Oct;18(5):896-899. DOI: 10.1161/01.str.18.5.896. PMID: 3629648.
    Studies suggest that hypertension may be more strongly associated with leukoencephalopathy than with deep infarcts. In acute stroke patients, leukoencephalopathy on CT should not be considered a fortuitous finding. Published in the journal of the American Heart Association / American Stroke Association (AHA/ASA).
  • Leukoencephalopathy with Vanishing White Matter from the National Library of Medicine's MedLinePlus. Leukoencephalopathy with vanishing white matter is a genetic progressive disorder that mainly affects the brain and spinal cord (central nervous system). This disorder causes deterioration of the central nervous system's white matter, which consists of nerve fibers covered by myelin. Myelin is the fatty substance that insulates and protects nerves.
  • "Progressive multifocal leucoencephalopathy in an immunocompetent patient with favourable outcome. A case report." by Halvor Naess, Solveig Glad, Anette Storstein, Christine H Rinaldo, Sverre J Mørk, Kjell-Morten Myhr & Hans Hirsch . BMC Neurology, 18May2010.

Persistent Memory in Cats is Created by Doing, Not by Seeing

Cynthia A. Lockley on

Cats remember where their paws have been. Researchers from the Department of Physiology at the University of Alberta, Edmonton, Alberta, Canada, report that cats can create memories of their environment without having to rely on vision. Stepping over and touching a physical obstacle with their forelegs creates a memory of the obstacle that persists for up to 10 minutes even after the obstacle is removed. Just seeing the obstacle does not appear to create a memory. The study found that visual memory lasts only a few seconds.

A cat's physical obstacle memory.
A cat's physical obstacle memory.

Keir G. Pearson studies the science of walking (the neurobiology of locomotion). For over 20 years, his test subjects included mice, cockroaches, locusts, humans, and felines. He is studying how animals learn to navigate complex environments, especially when they're moving around. His research has practical applications ranging from treating spinal cord injuries to building robots. "I'm interested in the general problem of how we remember the location of objects relative to the body as we move," Pearson says.

Over a 2-year period, Pearson compared cats' working memory of their recent movements with their visual memory and found that cats remember better with their bodies than with their eyes.

We put an obstacle in front of them and we stopped the cats after they stepped over it with their front legs, but not their back legs. We found that, even many minutes later, the cat would step high with their back legs, even though we had taken away the obstacle.

Pearson with his cat obstacle.
Keir Pearson with his cat obstacle. Credit: ExpressNews Staff, Univ. of Alberta
Felines' memories may in fact be longer but "many minutes" translates into about 10 minutes for the purpose of their experiments. Ten minutes is the maximum length of time Pearson and his fellow researcher David A. McVea were able to distract the animals, usually with a bowl of food.

To compare this working memory to the cat's visual memory, the researchers repeated the experiment, allowing the animals to see the obstacle (a small wooden block) but stopped them from moving forward before they made their first step over the obstacle.

The action of moving the front legs provided the information about the obstacle and the mechanism to establish a longer-term memory. The surprising thing to us was how short visual memory was. We thought it would last longer than a few seconds.

Similar research by Pearson's colleagues on other quadripeds such as dogs and horses, mirrored his results with cats exactly.

It's like driving; if you're a passenger, you really don't remember much about the trip, or the route, but if you've actually driven the car, you'll probably remember much better, and much longer.

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