Amygdala
Amygdala is a part of telencephalon and plays the most important role in emotional learning, reward, motivation (Cardinal, Parkinson et al. 2002, Berridge and Robinson 2003, Balleine 2005).(Laberge, Mühlenbrock-Lenter et al. 2006)
Due to its association with the regions involved in cognition (especially the neocortex and the hippocampus), the amygdala can affect cognition.The amygdala is also an important system in emotional computing.(LeDoux 1989)
The functional systems of the amygdala possess sensory input from early stations of the chemical senses (olfaction and taste), visceral sensory afferents and higher-order thalamic and cortical input from all sensory modalities, in addition to an output to autonomic and visceral centers in the brainstem and connections to the limbic cortex.(Laberge, Mühlenbrock-Lenter et al. 2006)
Neurobehavioral studies imply that, medial pallium of fishes probably have similar functions in emotional learning as well as amygdala; they are homologous structures. (Durán, Ocaña et al. 2010, Demski 2013, Duvarci and Pare 2014, Janak and Tye 2015, Uceda, Ocaña et al. 2015). The teleost amygdala is thought to reside in the medial region of the dorsal pallium (Dm) (Rink and Wullimann 2002, Northcutt 2006, Jesuthasan 2012)
Functional studies about the amphibian amygdala are rare; however, according to Swanson and Petrovich(Swanson and Petrovich 1998), the limbic associative component of the amphibian amygdaloid complex is not homologous to the frontotemporal cortical component of mammals since they have different developmental origins. Moreover it is indicated that amphibians do not possess a basolateral amygdaloid complex involved in the motivational effects of emotion(Cardinal, Parkinson et al. 2002). This implies that anamniotes have a limited repertoire of learning responses compared to amniotes.(Laberge, Mühlenbrock-Lenter et al. 2006)
The absence of aversive emotions (such as fever or increased heart rate)(Cabanac 1999, Paradis and Cabanac 2004) and taste aversion in fish and amphibians (Paradis and Cabanac 2004)due to the absence of basolateral amygdaloid complex, and also the participation of amygdala in emotional learning in mammals ,suggests that the advent of the basolateral amygdaloid complex and its reptilian equivalent have brought genuine innovations to vertebrates’ emotional behavior. (Laberge, Mühlenbrock-Lenter et al. 2006)
According Lanuza et al. (Lanuza, Belekhova et al. 1998)PDVR, the dorsolateral and the lateral amygdala are functionally similar to the mammalian basolateral complex. Thus, ADVR of reptiles is not part of the amygdala. However an alternative interpretation represents that the ADVR is homologous to the mammalian lateral nucleus of the amygdala. (Bruce and Neary 1995, Fernandez, Pieau et al. 1998). It is also suggested that, the PDVR of reptiles is involved in emotional behavior.(Tarr 1977, Distel 1978, Sugerman and Demski 1978, Laberge, Mühlenbrock-Lenter et al. 2006)
Amygdala in birds includes two regions: subpallial amygdaloid nuclei that is the nucleus taeniae of the amygdala (TnA) and the newly identified subpallial amygdala (SpA).(Yamamoto, Sun et al. 2005). In birds archistriatal structure, includes the posterior and medial archistriatum outlined Nucleus taenia (Tn) which is a discrete component. Based on hypothalamic formation, the posterior and medial archistriatum is homolog of amygdala in mammals.(Cheng, Chaiken et al. 1999) The part of amygdala in mammals which originated from ventral pallium is called pallial amygdala. Tn can demonstrate many of the structural and functional features of the amygdaloid complex in mammals. TnA receives olfactory input(Reiner and Karten 1985, Swanson and Petrovich 1998), hippocampal and hypothalamic output (Casini, Bingman et al. 1986, Canteras, Simerly et al. 1995, Cheng, Chaiken et al. 1999), enrichment in androgen and estrogen receptors (Martinez‐Vargas, Stumpf et al. 1976, Balthazart, Foidart et al. 1992, Balthazart, Foidart et al. 1998, Bernard, Bentley et al. 1999) and plays a tole in sexual behaviors (Thompson, Goodson et al. 1998, Cheng, Chaiken et al. 1999, Absil, Braquenier et al. 2002) as well as mammals so it specifically comparable to the mammalian medial nucleus of the amygdala (MeA). Nucleus taeniae of the amygdala (TnA) in birds responded to sounds and calls thus, amygdala plays role in vocalization..(Fujii, Ikebuchi et al. 2016)
SpA is comparable to extended amygdala (EXA) in mammalia since they have a similar location (ventral to globus pallidus (GP)).(Kitt and Brauth 1981, Martin Wild, Arends et al. 1990, Roberts, Hall et al. 2002, Reiner, Perkel et al. 2004) .(Yamamoto, Sun et al. 2005)
The amygdala of mammals influences physiological functions, and emotionally-laden social behavior (Aggleton 1992). The amygdala’s intricate networks of sensory inputs, motor outputs and interneurons mediate these vital functions. Afferent inputs to the amygdala contains monosynaptic projections from the olfactory bulb, subcortical sensory pathways, and hippocampal and other cortical connections (Ottersen 1982, Russchen 1982). The amygdala in mammals has a unique location for rapid detection and appraisal of events in the immediate environment That is important for rapid cognitive to respond swiftly in a life and death situation.(Cheng, Chaiken et al. 1999)
In rats lateral amygdala neurons respond to fear (LeDoux, Cicchetti et al. 1990). they also have some neurons that can vocalize different frequencies used possibly for different ends (Parsana, Li et al. 2012). In bats, the neurons in the lateral (Gadziola, Grimsley et al. 2011) or basolateral amygdala (Gadziola, Grimsley et al. 2011, Naumann and Kanwal 2011, Gadziola, Shanbhag et al. 2015) respond selectively to specific social calls. Furthermore, the arcopallium in birds can also respond to vocal sounds.
Subdivision structures and corresponding function of amygdala in avian and mammals are probably evolve in different ways.(Fujii, Ikebuchi et al. 2016)
In primates, amygdala appears almond shaped and is located in the anterior temporal lobe, toward its medial side. It receives projections from most cortical fields (Herzog and Van Hoesen 1976, Aggleton, Burton et al. 1980, Turner, Mishkin et al. 1980, Mufson, Mesulam et al. 1981, Friedman, Murray et al. 1986, Stefanacci and Amaral 2000), and usually returns them (Avendan, Price et al. 1983, Amaral and Price 1984, Carmichael and Price 1995, Ghashghaei and Barbas 2002). These anatomical facts, show the pivotal position of the amygdala in the telencephalon.(Murray 2007).