Communicating with the patient and often their relatives too, is a key component of the consultation process, more important now than ever. Patients derive benefits from a properly conducted listening and information exchange session which can often be improved by not only speaking their language but also appropriately using visual and other aids, or easily understood analogies. Computers are now ubiquitous within our society and their language and functions are understood by all groups including, increasingly, the older people by whom greater use is actively encouraged. Using computing-based analogies can, therefore, be very useful to explain and inform as an adjunct to properly honed communication skills.
The central processing unit is our brain. As we age, the associated hard drive becomes cluttered with fragmented information (our life), which can become increasingly difficult to access. We all know about the slowing recall with sought-for information often popping up later, we don't know exactly where to look. The search function of our operating system gets there in the end but takes a varying amount of time to build the screen piecemeal.
The function of memory is vulnerable to a range of pathological processes including neurodegenerative conditions associated with accumulations of proteinaceous materials, which can be fatal. The dementias, prion diseases, and others, are associated with amyloid plaques; a clogged-up system. In Alzheimer's disease for example, amyloid protein deposits are widespread throughout the cerebral cortex, hippocampus and amygdala, particularly the temporal lobe, together with a loss of nerve cells. Memory disturbances are often the most disabling feature of such conditions.1 Different forms of memory are dependent upon distinct neuroanatomic systems with episodic memory, explicit and declarative with easy recall, associated with the hippocampus. Memory loss due to dysfunction affects the most recent memories as they are the most vulnerable, whereas remote memories are more resistant. The problem is one of getting information both in to and out of storage coupled with an impossibility to retain recent items, described as a dysfunctional ‘recent memory file cabinet’, which is associated with poor activation and retrieval. Working memory is also explicit and declarative and many neurodegenerative diseases impair working memory tasks.2
With the Random Access Memory (RAM) of our computer, the immediate access, recent, volatile memory is most vulnerable. With speed and consistency, RAM is used as the main memory or primary storage, with the working area used for loading, displaying, and manipulating applications and data. In most personal computers, the RAM is not an integral part of the central processing unit apart from a small amount, cache memory. Remote (permanent) memories are more resistant and reside on the hard drive.
The problem of both getting information in to and out of storage, together with the failure to retain recent information, poor activation and retrieval, and a dysfunctional ‘recent memory file cabinet’ are features of ‘RAM disease’. The size of RAM can be likened to a person's IQ. Those patients with a smaller IQ notice its dysfunction less, whereas those with a higher IQ, and who use it to the full, are hit hard by even early dementia. RAM, of course, must be used well and looked after with good diet, exercise both mental and physical, and the avoidance of abuse to keep it in tip-top condition.
Short-term memory decay, for whatever reason, means that less is available. The long-term storage area, the hard drive, is then increasingly used when there is insufficient RAM and too many open applications; dipping in and out is inefficient and slow, a greater problem when the hard drive is fragmented and full. In your computer, RAM dysfunction can be easily corrected by adding new memory or RAM sticks, which can then be quickly removed and replaced when they become damaged or too small for your current needs. For the patient, however, it's not so easy, but drugs may delay or reduce the variable rate of natural deterioration and postpone overt RAM disease, while others may serve to recruit or refresh and bring a closed, locked-in patient back online. The end of RAM is analogous to the clinical end stage.
Patients may also ask their GP about post-operative cognitive dysfunction (POCD) which typically affects older patients, about 10% of those over 60 years and about one in three of those over 80 years following surgery.3 Long-term, even permanent, neuronal damage and neurological change occurs in the ageing brain leading to problems of storage and recall of memory and cognitive processing. Failure to perform simple tasks, forgetting (more ‘senior moments’), and difficulties with crosswords, are examples.3 Episodic memory systems depend upon the medial temporal lobes including the hippocampus,1 and POCD in rats is found to be associated with this area by a different mechanism.4
Computer-operating system crashes are well understood, occurring when the operating system has lost its internal self-consistency and can be caused by either physical damage to the storage device or, more commonly, logical damage to the file system. A less common power problem is an outright power loss which can be brief or last several hours. Older systems' analogue power supplies are unable to handle this, but most computer power supplies today have a greater ability to cope. Power loss (longer than about 10 milliseconds), however, not only loses data since the last ‘save’, but, if writing to a disk at the time of loss, results in data corruption by preventing file system structures from being completely written to the storage medium, potentially damaging the medium itself. If disk file systems become corrupted, the result is that the file system is left in an inconsistent state, which can cause a variety of problems including unusual behaviour, system crashes, or an actual loss of data. The hard drive or portable storage medium may not be recognised when power comes back into the system and at the same time, the equipment could also be damaged by a power surge.
General anaesthesia can be considered analogous to an outright power loss with a duration from minutes to many hours. Older patients (with analogue systems?) cannot handle this well, but power supplies of newer models do so better. Loss of power not only loses your data since the last save, but, if writing data to a disk at the time of failure, would cause data corruption and potentially harm the storage medium; a situation which can be said to be analogous to the fully conscious patient in the anaesthetic room today before induction of general anaesthesia. The corrupted inconsistent state of the ‘file system’ can cause a variety of problems, such as strange behaviour, confusion, and actual loss of data, ‘Dad just wasn't the same after his operation’. When the power returns, the patient ‘wakes up’ often by the equivalent of a power surge in sensory input terms with pain, or by the use of stimulant or antagonist drugs.
In rats, a hippocampal inflammatory response has now been found in association with POCD,4 and amyloid protein accumulations in vitro with the anaesthetic agent isoflurane.5 It may be more of a problem in those patients whose hippocampus is simply starting to fill up with proteinaceous material on the way to dementia. Unfortunately, POCD cannot be prevented by avoiding general anaesthesia as the incidence following regional anaesthesia is essentially the same. I suspect that this may be due to gross interference following central neuraxial (spinal and epidural) blocks with the activity of the reticular arousal system which, through its ascending connections, ensures the responsiveness of the cerebrum facilitating data processing, and maintains the ability to filter all the information around us.
For those patients with slightly moth-eaten primary storage or an old operating system, the vista does not need to be entirely bleak. Patients with RAM disease may be helped by looking into back-up storage and working to ensure that documents and files are easy to find, which may not require the use of pharmaceuticals. A managed or gradual shut-down of the system by drugs or other means prior to general anaesthesia may reduce the incidence of POCD, as may the use of more limited regional anaesthesia techniques.
- © British Journal of General Practice, 2007.
