Does caffeine actually enhance cognition?

Question

I have heard, respectively:

• Caffeine measurably enhances cognitive function.
• Caffeine does not measurably enhance cognitive function in any significant way.
• Caffeine enhances cognitive function, but only indirectly, in that it counteracts the effects of fatigue.
• Caffeine enhances cognitive function, but only indirectly, in that it counteracts the effects of caffeine withdrawal.
• Caffeine has no physical effect on cognitive function, but has a psychological effect.

What is the actual behavior of caffeine in relation to cognition? (I'm particularly interested to know if any research addresses the claim that it only counteracts the effects of caffeine withdrawal)

Answer 1

In a study by Wight et al. (2013) ^[1] it was shown that bees feeding on nectar containing caffeine seem to enhance the bees' memory of those flowers. They hypothesized this based on the fact that:

Two caffeine-producing plant genera, Citrus and Coffea, have large floral displays with strong scents and produce more fruits and seeds when pollinated by bees (8, 9)

They tested this hypothesis by feeding bees sucrose solutions with different concentrations of caffeine and measured their behavioural response.

We hypothesized that caffeine could affect the learning and memory of foraging pollinators. To test this, we trained individual honeybees to associate floral scent with 0.7 M sucrose and 7 different concentrations of caffeine and tested their olfactory memory. Using a method for classical conditioning of feeding responses (proboscis extension reflex, 11), bees were trained for 6 trials with 30 s between each pairing of odour with reward. This inter-trial interval approximated the rate of floral visitation exhibited by honeybees foraging from multiple flowers on a single Citrus tree (see methods). The presence of low doses of caffeine in reward had a weak effect on the rate of learning (Fig. 2A), but it had a profound effect on long-term memory. When rewarded with solutions containing nectar-levels of caffeine, three times as many bees remembered the conditioned scent 24 h later and to responded as if it predicted reward (Fig. 2B, logistic regression, χ72 = 41.9, P < 0.001). Twice as many bees remembered it 72 h later (Fig. 2C). This improvement in memory performance was not due to a general increase in olfactory sensitivity resulting from caffeine consumption (Fig. S2A). In fact, the effect of caffeine on long-term olfactory memory in bees was greater than that produced by high concentrations of sucrose when the same experimental methods were used (e.g. 2.0 M, Fig. S2B).

However, bees would not prefer nectar (or sugar solutions, as at higher concentrations (>1mM) as they would find it distasteful.

I am not sure if this hypothesis is extensible to higher organisms. It may have some effects on alertness and attention but there are no stringent studies to assess its effects on learning.

This review ^[2] on the possible cognitive effects of caffeine concludes that:

Thus, caffeine apparently cannot be considered a 'pure' cognitive enhancer. Its indirect action on arousal, mood and concentration contributes in large part to its cognitive enhancing properties.

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<sup>[1] Wright, G. A., et al. "Caffeine in floral nectar enhances a pollinator's memory of reward." Science 339.6124 (2013): 1202-1204.

[2] Nehlig, Astrid. "Is caffeine a cognitive enhancer?." Journal of Alzheimer's Disease 20.S1 (2010): 85-94.</sup>

Answer 2

Caffeine response is dependant on the individual. Caffeine has a very similar chemical make-up to adenosine which your body uses to transfer the energy you eat into energy your body can actually use (chemical energy). When your body has enough adenosine, it begins what is called a negative feedback cycle that stops adenosine production and sustains homeostasis. The feedback loops works by delivering a signal to put the body in a regenerative phase upon further adenosine binding. However, caffeine, being the wonderful individual that it is, disrupts that negative feedback loop and continues the conversion of excess (eaten) energy to chemical energy. But where in your body its dispersed is dependant on the individual.

The conversion to chemical energy is indirect though. Since adenosine is a principal neuromodulator, it actually tricks your body into behaving as it would at your most natural wakeful state. For example: Glutamate, GABA, norephinephrine, serotonin and acetylcholine are all inhibited by adenosine build-up at A1 receptors (a type of adenosine receptor) but caffeine stops adenosine from inhibiting these neurotransmitters. These five neurotransmitters all assist in metabolism (Glutamate is an essential compound in cellular metabolism).

Caffeine will never give you energy, it just uses your energy faster, in fact it probably causes energy debt from the work your body does to flush out the toxin.

In short: Yes it can enhance cognition, if the extra ATP (energy molecule made from adenosine) is carried to the brain. As it is not a homeostatic process it's difficult predict.

When the body is constantly put out of it's homeostasis, it adapts the toxin into its homeostatic balance (kind of like a beat em' or join em'). In this way, an individual's body begins to need the caffeine to function normally. Caffeine dependance is very low however, since it has been around for centuries, we've evolved to know it as a toxin but to not depend on it.

References:

J Alzheimers Dis. 2010;20 Suppl 1:S3-15. doi: 10.3233/JAD-2010-1379.

http://thebrain.mcgill.ca/flash/a/a_11/a_11_m/a_11_m_cyc/a_11_m_cyc.html

http://pharmrev.aspetjournals.org/content/51/1/83.short