depression
Depression not only has bland taste but bland sense of smell too
Jan 4th
In one of my earlier post on depression, I had commented on the fact that those suffering from depression have less sensitivity to sweet and bitter tastes and as such may compensate by eating more sugar thus leading to the well documented diabetes – depression linkage.
In a new study it has just been discovered that not only depressives have bland sense of taste, their sense of smell is also diminished and they may make compensations by using greater amounts of perfume. Overall it seems that those suffering from depression will have bland subjective experience of flavor(which is a combination of both smell and taste) and thus may even not really find what they eat to be tasty.
To me, this is an important finding. To my knowledge no research has been done in other sense modalities (like vision), but there is every reason to think that we may discover a bland sense of vision in depression. Why do I surmise so? this is because there is extensive literature available regarding the manic state and how things seem ‘vivid’ during that state including visual vividness. If depression is the converse of Mania, it follows that a corresponding blandness of vision should also be observed in those who are clinically depressed.
We also know that in extreme or psychotic forms of Mania, auditory hallucinations may arise. I am not suggesting that hallucinations are equal to vividness, but I would definitely love to see studies determining whether the auditory sense is heightened in Mania (maybe more absolute pitch perception in Mania) and a corresponding loss of auditory absolute pitch perception in depression. If so found, it may happen that music literally becomes subdued for people with depression and they sort of do not hear the music present in everyday life!
Whether other sense like touch, vestibular/ kinesthetic , proprioception (a heightened sense of which may give rise to eerie out-pf-body experiences in Mania) are also diminished in depression is another area where research may be fruitful.
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Disscoiation between analgesic and addictive effects of pain-killers
Aug 22nd
Common pain-killers like Morphine have both pair-relieving as well as tolerance and addictive effects. Opiates, it had been theorized earlier, were able to relieve pain via a mechanism that involved the neurotransmitter Serotonin. For the first time , this has been decisively proved to be so, by examining the effects of pain-killer on mice that were engineered to have the serotonin producing gene, Lxmb, silenced in the 5-HT neurons. As such these mice completely lacked serotonin in their brains.
It was found that these mice exhibited more sensitivity to pain and also morphine, or other opiates, were not able to relive the pain in these mice. On the other hand the addictive effects of morphine remained intact.
I am tempted to conjecture further. Is it the case that psychological and physical pain share the same neural substrates? Remember that low levels of serotonin cause depression, in which the sensitivity to psychological pain is elevated. this is similar to the fact that the sensitivity for physical pain is heightened in mice lacking serotonin.I am further tempted to stick my neck out and recommend that the experiment be perormed with mice that have dopamine producing neurons silenced in the brain. If such mice can survive to adulthood, would they exhibit the analgesic effects of morphine, but not its addictive effects? anyway this dissociation between analgesic and addictive effects of morphine would have serious pharmacological effects.
TMS causes nurogenesis and LTP in the mice brain!
May 24th
Transcranial Magnetic Stimulation (TMS) has been shown to be effective in treating depression and schizophrenia , but the exact mechanisms were unknown. TMS is nomally utilized for ‘knocking off’ activity of a brain region near the skull. If this brain area serves an inhibitory function, TMS would lead to more activation in some other connected areas of the brain and vice versa.
As per this blurb from the New Scientist, Battaglia and colleagues found that repeated TMS application to mice hippocampus (dentate gyrus) over a period of 5 days lead to more stem cell neurons there and also lead to strengthening of existing synaptic connection by means of Long Term Potentiation(LTP). It should be noted that hippocampus is one of the prime areas in human brain where neurogenesis happens.
I have blogged earlier regarding the depression-as-low-neurogenesis-in-hippocampus theory and this finding seems to support that theory and provides a mediating mechanism of neurogenesis via which TMS may be leading to alleviation of depression. The researchers also believe that this finding would help in making devices that could lead to alleviation of learning and memory problems like that faced in the Alzheimer’s.
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Depression, Neurogenesis and Spatial navigation
Mar 28th
We all know that hippocampus is the seat of both memory as well as spatial abilities (cognitive map theory). We also know that most of the neurogeneisis in adult humans happens in hippocmapus. We also know that depression is caused by stress and both stress and depression lead to or are correlated with reduced neurogeneisis in the hippocmapus (my learning helplessness theory of depression) .
Now a new study has found that depressed people have impaired spatial navigation abilities. Putting 2 and 2 together it is highly plausible that this relationship between depression and impaired spatial navigation is mediated by the reduced neurogeneies or atrophy in hippocampus.
Relatedly, a good article (pdf) regarding how new anti-depressants are targeting neurogenesis in hippocampus as a mechanism to alleviate depression.
Three cheers to the cognitive map theory- the focus with which this blog started!!
Hat Tip: BPS Research Digest
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The Mind – Brain dichotomy: What it means to have a mind
Feb 28th
Researchers at Harvard, Gray et al, are conducting an ongoing mind survey, and have also reported some findings from that online survey, based ona asmaple of more than 2,000 people.
The survey attempts to make one think about different forms of entities that may have a mind and to assign different degrees of consciousness/ mind on them.
Gray worked alongside fellow psychologists Heather Gray and Daniel Wegner on the study, which presented respondents with 13 characters: 7 living human forms (7-week-old fetus, 5-month-old infant, 5-year-old girl, adult woman, adult man, man in a persistent vegetative state, and the respondent himself or herself), 3 non-human animals (frog, family dog, and wild chimpanzee), a dead woman, God, and a sociable robot.
Participants were asked to rate the characters on the extent to which each possessed a number of capacities, ranging from hunger, fear, embarrassment, and pleasure to self-control, morality, memory and thought. Their analyses yielded two distinct dimensions by which people perceive the minds of others, agency and experience.
The participants attribute different degrees of these factors to the characters based on a forced choice between a pair of characters on a particular ability related to a mind capacity like feeling fear or making moral decisions. I believe they than id factor analysis or some such statistical method to come up with two independent dimensions or factor underlying the concept of mind: Agency or Experience.
Agency seems to be related to the fact that people (entities with mind) can take volitional actions and are thereby responsible for their actions. They can thus also be judged morally based on their actions and the choices they make.
Experience seems related to the fact that people (entities with mind) have an ability to feel and are emotional entities that have subjective experience of emotions like pain, fear and hunger and also have desires, longings and feelings etc.
The ability to perceive qualia surprisingly didn’t come out as a separate entity and consciousness or ability to perceive qualia is supposedly covered under the Experience factor.
These dimensions are independent: An entity can be viewed to have experience without having any agency, and vice versa. For instance, respondents viewed the infant as high in experience but low in agency — having feelings, but unaccountable for its actions — while God was viewed as having agency but not experience.
“Respondents, the majority of whom were at least moderately religious, viewed God as an agent capable of moral action, but without much capacity for experience,” Gray says. “We find it hard to envision God sharing any of our feelings or desires.”
The regular readers of this blog will remember that one of the important distinction that I hypothesized between Schizophrenia and Autism was that due to agency: with schizophrenics attributing too much Agency; and Autistic attributing too less Agency to others (other people or other entities that may have mind). Also as God is perceived as having too much Agency, but not much Experience, thus when the Schizophrenia end of spectrum kicks in, they may also attribute too much agency to themselves and feel God-like or Divine. The negative symptoms related to less of experience would also fit the fact of being God-like or being an angel/ special person and thus not having too much emotions. The Autistic end of the spectrum however would be guided by too-less-mind sort of attributions and thinking; and thus they may view themselves and others as brains and not minds. They might thus be more capable with inanimate objects and rules of nature (thus making them good scientists/ engineers/ systemizers) ; but poor at social/ ethical aspects that require attributing minds to animals for example.
One should also distinguish between the two dimensions of Agency and Experience. Thus Autistic may have a defect due to Agency, but may have mirror neurons or other systems that confer on them the ability to feel , not only subjective feelings of self – but empathetic feelings of others too.
Also, it has been this blogs contention that the Dimension of experience is best seen as a dimension on one end of which is the Bipolar patients and on the other end of which is the Deprosanalisation/ apathetic / derealization spectrum. while the Bipolar feels too much emotions and motivations; the depersonalised/ derealized person may show too less emotion/ motivation.
Thus in mind at one end we have people having too much mind/ believing in too much mind (and exemplified by Schizophrenic and Bipolar ) and at the other end we have too people having too much brain/ believing in too much brain (exemplified by Autistic/ depersonalised people). One gives great Art, the other great Science.
Returning to the current study:
“The perception of experience to these characters is important, because along with experience comes a suite of inalienable rights, the most important of which is the right to life,” Gray says. “If you see a man in a persistent vegetative state as having feelings, it feels wrong to pull the plug on him, whereas if he is just a lump of firing neurons, we have less compunction at freeing up his hospital bed.”
This is exactly one of the pertinent point made by the film Munnabhai MBBS- that coma patients have feelings and have a right of life. While I have featured the effects of Lage Raho Munnabhai earlier; I would also like to pay tribute to its prequel/ precursor.
On that note, let us keep our antennas up for how thinking about us as entities with Agency and Experince can lead to Art; while thinking of us as brains can lead to good scince. I’m sure you’ll agree that we need both of these concepts about us humans.
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