Hormones and chemicals
some areas of the brain have the capability to express the receptors of
the hormones which influence behavior.(Crews, Sanderson et al. 2010).
Hormonally mediated events have crucial roles in central nervous system
development and function. Changes in cognitive function therefore, might
be correlated with different kinds of hormones.(Schantz and Widholm
2001)
Invertebrates have a hormonal system like vertebrates. There are also
hormonal receptors in their nervous system. Each hormone has a specific
function and as hormones evolve, behaviors and memory and cognition
expand (Lockard, Ebert et al. 2017) (Gruber 2014)
Hormonal, neuropeptide and oxytocin signals are seen in some
invertebrates; these hormones are involved in memory and learning.
Oxytocin enhances neurotransmission and metabolism. The function of this
hormone in invertebrates is similar to its function in the human brain.
In Protostomia, for example, there are families that have oxytocin and
vasopressin. Both of these hormones are found in modern cephalopods,
octopus and cuttlefish. (Minakata 2010) Serotonin is also found in
invertebrate drainage to mammals. Genetically dense invertebrates are
suitable models for explaining the complexity of serotonin signal
pathways. These models explain how serotonin and neuronal structure
influence behavior. From these explanations one can conclude how
serotonin affects human cognitive function. (Curran and Chalasani 2012)
Oxytocin and its nonmammalian homologues (for example isotocin) have an
important role in modulating social behaviors and emotions. Oxytocin in
mammals influences social behaviors that do not necessarily benefit the
individual(Barraza, McCullough et al. 2011). Mesotocin, a homologue of
oxytocin in birds, has a similar role for demonstrating social
behavior(Goodson, Schrock et al. 2009). for example many corvids share
their food voluntary which is an example for prosocial behavior(De Kort,
Emery et al. 2006, von Bayern, de Kort et al. 2007, Scheid, Schmidt et
al. 2008, Ostojić, Shaw et al. 2013, Duque and Stevens 2016).(Duque,
Leichner et al. 2018)
Fish, in response to emotional stimuli, produce cortisol (Bonga). Some
transmitter substances are identified in fish such as dopamine,
serotonin and isotocin which are associated with emotional behaviors
like reward and mood in humans. (Winberg and Nilsson 1993, Thompson and
Walton 2004, Kittilsen 2013)
The role of gonadal hormones in the development of brain areas involved
in reproduction has been indicated in many studies (Schantz and Widholm
2001). They play important roles in social behaviors and mating
processes.
Recently it has been indicated that early exposure to estrogens and
androgens has important functions brain regions not involved in
reproduction. One of these is the hippocampus, which plays an important
role in learning and memory, particularly spatial learning and
memory(McEwen, Gould et al. 2007). Sex differences in spatial learning
have been reported. For instance, Male rodents have less mistakes than
females on spatial learning and navigating. According to Williams et al.
(Williams, Barnett et al. 1990)these differences could be due to
differences in the way males and females process spatial information.
Steroid hormone also controls some parts of spatial learning and memory
ability in mammals (Gouchie and Kimura 1991, Williams and Meck 1991,
Roof 1993). In birds, testosterone and estradiol can influence spatial
memory (Hodgson, Meddle et al. 2008). Additionally, sex hormones in
juvenile birds can affect vocal learning (Bottjer and Johnson 1997). for
example among young male swamp sparrows those which are able to copy
more syllables, have higher levels of estradiol.(Marler, Peters et al.
1987)
Finally, Thyroid hormone plays an important role in neurobehavioral
functions, such as delayed reflex development, and emotionality, and
deficits in learning and memory (Davenport 1976, De Kloet, Rosenfeld et
al. 1988, Akaike, Kato et al. 1991, Stein, Adams et al. 1991).