What is visuospatial working memory?
In Baddeley's model of working memory, there is a component called the visuospatial sketchpad, responsible for temporarily holding visual and spatial information: the location of objects, the route through a city, the arrangement of chess pieces on a board. It is distinct from verbal memory (Digit Span) and has its own neural mechanisms, primarily in the right parieto-occipital cortex.
The Corsi test, developed at McGill University in 1972 by Philip Corsi, became the gold standard for assessing this capacity. It is included in major clinical batteries such as the WMS (Wechsler Memory Scale) and CANTAB (Cambridge Cognition). Lesion studies have shown that Corsi forward depends on the right parieto-occipital region, while Corsi backward additionally involves the prefrontal cortex (manipulation in working memory).
Forward vs backward: the difference
| Aspect | Forward | Backward |
|---|---|---|
| Dominant process | Passive storage | Active manipulation |
| Mean adult span | 5–6 | 4–5 |
| Brain region | Right parieto-occipital | + Prefrontal |
| Sensitivity to ageing | Moderate | High |
Frequently asked questions
▶What is the Corsi test?
The Corsi Block-Tapping Test was developed in 1972 by Philip Michael Corsi to evaluate visuospatial working memory. The examiner taps blocks in a particular order and the patient must reproduce the sequence. The original version uses 9 wooden blocks arranged randomly on a board; digital versions (CANTAB Cambridge Cognition, WMS-III) use 9–16 squares on screen. The span (the maximum sequence length successfully reproduced) is the primary measure.
▶What is a normal Corsi span?
For healthy adults, the mean span is 5–6 (Kessels et al. 2000). Adults over 65 typically have a span of 4–5 forward and 3–4 backward. A forward span below 4 in adults under 70 may indicate a visuospatial working memory deficit worth investigating clinically. A large difference between forward and backward (more than 2 units) suggests difficulties with information manipulation, not just storage.
▶What is the difference between forward and backward?
Forward primarily tests passive storage — retaining the sequence in short-term memory. Backward additionally tests active manipulation — you must mentally reverse the sequence before reproducing it. Backward is more sensitive to frontal dysfunction (prefrontal cortex). We recommend trying both for a complete assessment.
▶Does age affect the score?
Yes, but not dramatically. Visuospatial memory declines more slowly than processing speed. Normative data show a decrease of approximately 0.5–1 span between age 50 and 80. It is important to compare against your own previous score, not a fixed norm — individual variability is large.
▶Can I use this test to assess a parent with Alzheimer's?
Not for diagnosis — that requires a complete clinical evaluation with a neuropsychologist. For informal tracking, yes: a span that consistently drops from 5 to 3 over 6–12 months is a signal worth discussing with a doctor. We also recommend the NursingHelp app, which allows historical tracking and automated family alerts.